The dwarf planet Ceres, which orbits the sun in the asteroid belt between Mars and Jupiter, is a unique body in the solar system, bearing many similarities to Jupiter’s moon Europaand Saturn’s moon Enceladus, both considered to be potential sources for harboring life.
“I think of Ceres actually as a game changer in the solar system,” Schmidt said.
“Ceres is arguably the only one of its kind.”
The innermost icy body
When Ceres was discovered in 1801, astronomers first classified it as a planet. The massive body traveled between Mars and Jupiter, where scientists had mathematically predicted a planet should lie. Further observations revealed that a number of small bodies littered the region, and Ceres was downgraded to just another asteroid within the asteroid belt. It wasn’t until Pluto was classified as a dwarf planetin 2006 that Ceres was upgraded to the same level.
Ceres is the most massive body in the asteroid belt, and larger than some of the icy moons scientists consider ideal for hosting life. It is twice the size of Enceladus, Saturn’s geyser-spouting moon that may hide liquid water beneath its surface.
Unlike other asteroids, the Texas-sized Cereshas a perfectly rounded shape that hints toward its origins.
“The fact that Ceres is so round tells us that it almost certainly had to form in the early solar system,” Schmidt said. She explained that a later formation would have created a less rounded shape.
The shape of the dwarf planet, combined with its size and total mass, reveal a body of incredibly low density.
“Underneath this dusty, dirty, clay-type surface, we think that Ceres might be icy,” Schmidt said. “It could potentially have had an ocean at one point in its history.”
“The difference between Ceres and other icy bodies [in the solar system] is that it’s the closest to the sun,” Castillo-Rogez said.
Less than three times as far as Earth from the sun, Ceres is close enough to feel the warmth of the star, allowing ice to melt and reform.
Investigating the interior of the dwarf planet could provide insight into the early solar system, especially locations where water and other volatiles might have existed.
“Ceres is like the gatekeeper to the history of water in the middle solar system,” Schmidt said.
Studying the surface
As large as Ceres is, its distance has made it a challenge to study from Earth. Images taken by the space-based Hubble Space Telescope provided some insight to its surface, but to be sighted, features could be no larger than 25 kilometers (15.5 miles) in diameter.
Several round circular spots mar the terrain, features which Schmidt said could be any one of a number of geologic terrains, including potentially impact basins or chaos terrains similar to those found on Europa. The largest of these, named Piazzi in honor of the dwarf planet’s discoverer, has a diameter of about 250 km (155 miles). If this feature is an impact basin, it would have been formed by an object approximately 25 km (15.5 miles) in size.
But for Schmidt, this is another possible indication about the dwarf planet’s surface.
“It doesn’t mean that Ceres hasn’t been hit by something bigger than 25 kilometers,” she said. “It just means that whatever is going on on Ceres has totally erased [the topographic signature of that event].”
Ceres may have suffered major impacts, especially during periods of heavy bombardment early in the solar system’s history. If the surface contained ice, however, those features may have been erased.
Telescopes on Earth have also been able to study the light reflecting from the planet and read its spectra.
“The spectrum is telling you that water has been involved in the creation of materials on the surface,” Schmidt said.
The spectrum indicates that water is bound up in the material on the surface of Ceres, forming a clay. Schmidt compared it to the recent talk of mineralsfound by NASA’s Curiosityon the surface of Mars. [The Search for Life on Mars (A Photo Timeline)]
“[Water is] literally bathing the surface of Ceres,” she said.
In addition, astronomers have found evidence of carbonates, minerals that form in a process involving water and heat. Carbonates are often produced by living processes.
The original material formed with Ceres has mixed with impacting material over the last 4.5 billion years, creating what Schmidt calls “this mixture of water-rich materials that we find on habitable planets like the Earth and potentially habitable planets like Mars.”
A prime site for life?
Water is considered a necessary ingredient for the evolution of life as we know it. Planets that may have once contained water, such as Mars, as well as moons that could contain it today, like Enceladus and Europa, are all thought to be ideal for hosting or having once hosted life.
Because of its size and closeness, Schmidt calls Ceres “arguably more interesting than some of these icy satellites.”
“If it’s icy, it had to have an ocean at some point in time,” she said.
Castillo-Rogez compared Earth, Europa, and Ceres, and found that the dwarf planet bore many similarities to Earth, perhaps more than Jupiter’s icy moon. Both Earth and Ceres use the Sun as a key heat source, while Europa takes its heat from its tidal interaction with Jupiter. In addition, the surface temperature of the dwarf planet averages 130 to 200 degrees Kelvin, compared to Earth’s 300 K, while Europa is a frosty 50 to 110 K.
“At least at the equator where the surface is warmer, Ceres could have preserved a liquid of sorts,” Castillo-Rogez said.
Liquid water could exist at other points on the dwarf planet known as cold traps, shadowed areas where frozen water could remain on the surface. Such icy puddles have been found on Earth’s moon. [Photos: Europa, Mysterious, Icy Moon of Jupiter]
“The chemistry, thermal activity, the heat source, and the prospect for convection within the ice shell are the key ones that make us think that Ceres could have been habitableat least at some point in its history,” Castillo-Rogez said.
The future of Ceres
As scientists develop more information about Europa and Enceladus, there has been a greater call to investigate the two prime sites for life. But Schmidt and Castillo-Rogez think that Ceres could also be a great boon for astrobiology and space exploration.
“It’s not a difficult environment to investigate,” she said. “As we think about the future of landed missions for people and rovers, why not go to Ceres?”
Though it would be more challenging to drill into than Europa, which boasts an icy surface layer, the dwarf planet would make a great site to rove around on. Schmidt also noted that it could make a great launching point when it comes to reaching the outer solar system. Its smaller mass would make it easier to land on — and leave — than Mars, which could make it a good site for manned missions.
“We have such a big planet bias, we have such a bias for things that look exactly like us,” Schmidt said.
“In this kind of special place in the solar system, we have a very unique object that might be telling us a lot about what we don’t know about building a habitable planet.”
NASA’s Dawn mission launched September 27, 2007. It traveled to the asteroid Vesta, where it remained in orbit from July 2011 to July 2012 before heading to Ceres. It is slated to spend five months studying the dwarf planet, though Schmidt expressed hope that the craft would continue working beyond the nominal mission, allowing the team to study the icy body even longer.
Castillo-Rogez pointed out that not only will Dawn reach Ceres in 2015, the European Space Agency’s Rosetta spacecraft will be escorting the comet Churyumov-Gerasimenko around the sun that year, while NASA’s New Horizons mission will be reaching Pluto and its moon Charon.
“’15 is going to be a great year for icy bodies,” Castillo-Rogez said.
“I think when we get to Ceres, it’s just going to be an absolute game changer, a new window into the solar system that we wouldn’t have without going there,” Schmidt said.
The space agency announced on Thursday that it’s teaming with Worcester Polytechnic Institute to challenge teams from academia and industry to build a smart robot that can locate and retrieve geologic samples while maneuvering over rugged terrain on an asteroid or Mars.
Registration is open for the competition that will be judged in June 2014. For the challenge, dubbed the Sample Return Robot, NASA is putting up the $1.5 million in prize money, which will be dispersed among teams who complete certain levels of the competition. More information is available from the WPI website.
“The objective of the competition is to encourage innovations in automatic navigation and robotic manipulator technologies that NASA could incorporate into future missions,” said Michael Gazarik, NASA’s associate administrator for space technology, in a statement. “Innovations stemming from this challenge may improve NASA’s capability to explore an asteroid or Mars, and advance robotic technology for use in industries and applications here on Earth.”
This isn’t the first time NASA has looked outside its own walls for robotic assistance. Earlier this year, the space agency awarded $5,000 to Team Survey of Los Angeles for successfully completing a 2013 Sample Return Robot Challenge. NASA noted that it expects the 2014 challenge will advance progress already made and expand the field of competing teams.
NASA wants to advance its robotics technology, which has been behind much of its exploration of Mars.
3D printing could help the asteroid-mining industry get off the ground.
Billionaire-backed asteroid-mining company Planetary Resources is teaming up with 3D Systems, whose 3D printing technology will help craft components for the Arkyd line of prospecting spacecraft, officials announced Wednesday (June 26).
The collaboration should help Planetary Resources build certain parts of its Arkyd 100, 200 and 300 probes more cheaply and efficiently, officials said. [Planetary Resources' Asteroid Mining Plan (Photos)]
“We are excited to work very closely with Planetary Resources’ engineering team to use advanced 3D printing and manufacturing technologies to increase functionality while decreasing the cost of their Arkyd spacecraft,” 3D Systems CEO Avi Reichental said in a statement.
“In success, we will create the smartphone of spacecraft and transform what has been an old-style, labor-intensive process into something very scalable and affordable that will democratize access to space, the data collected from space and off-Earth resources for scientists and the public,” Reichental added.
Planetary Resources co-founder Peter Diamandis said that the use of 3D printing in the production of the Arkyd spacecraft series could help the company achieve its lofty goals.
“We are absolutely thrilled to partner with 3D Systems, the world’s pioneer and leader in 3D printing and advanced manufacturing, as we pursue our vision to expand the resource base beyond Earth,” Diamandis said in a statement. “3D Systems has a long history of inventing, advancing and democratizing manufacturing – and our vision of mass producing the Arkyd 100, 200 and 300 line will greatly benefit from their thinking and technology.”
Planetary Resources officials hope to launch a series of robotic spacecraft into Earth orbit and, eventually, to near-Earth asteroids in order to mine them for resources such as precious metals and water.
The company, which counts Google execs Larry Page and Eric Schmidt among its investors, hopes its efforts help open up the solar system to further human exploration.
The Arkyd 200 and 300 spacecraft will be able to both search for asteroids and fly toward promising targets for closer inspections. Once an asteroid is spotted, Planetary Resources plans to send a group of about five Arkyds out to the space rock, Diamandis said during a recent Google+ Hangout.
The Arkyd 100, on the other hand, will scout for space rocks from Earth orbit.
The first Arkyd 100 is expected to launch in 2015. Planetary Resources has pledged to make one of these satellites the first publicly accessible space telescope ever sent into orbit. The telescope will search for asteroids and take “space-selfies” crafted from user-submitted photos.
Nearly 15,000 people have contributed more than $1.2 million to help build Planetary Resources’ Arkyd 100 through the crowdfunding website Kickstarter. Planetary Resources’ Arkyd 100 Kickstarter campaign ends on June 30 at 10 p.m. EDT (0200 July 1 GMT). To mark the end if the Kickstarter campaign, Planetary Resources will hold a three-hour webcast Sunday beginning at 6 p.m. EDT (3 p.m. PDT/2200 GMT) to present its asteroid-mining efforts to the public.
If the campaign reaches $1.7 million, Planetary Resources has pledged to create an “Asteroid Zoo” project in cooperation with Zooniverse, a citizen-science website that helps connect the public with projects in different fields. According to the company, the Asteroid Zoo is envisioned to be “a program to allow students, citizen scientists and space enthusiasts to find potentially hazardous asteroids (PHAs) at home and help train computers to better find them in the future.”
“Planetary Resources values the power of the connected mind; when working together, we can accomplish much more than any of us can do alone,” Chris Lewicki, President and Chief Engineer for Planetary Resources, said in a statement. “We’re creating this program to harness the public’s interest in space and asteroid detection, while providing a very real benefit to our planet.”
The existence of the distant exoplanets, called Kepler-62e and Kepler-62f, was unveiled during a NASA press conference on April 18th. The two worlds are perhaps the most promising life-hosting candidates yet found beyond our solar system, their discoverers said. Computer models suggest both planets are covered by uninterrupted oceans, which could theoretically support a wealth of aquatic lifeforms.
“Look at our own ocean — it is just absolutely full of life,” said Bill Borucki of NASA’s Ames Research Center in Moffett Field, Calif., leader of the team that discovered the two exoplanets. “We think, in fact, life [on Earth] might have begun there.” [Habitable Super-Earths Ideal for Life (Gallery)]
Borucki is science principal investigator of NASA’s Kepler space telescope, which spotted Kepler-62e and f. The two alien worlds are 1.6 and 1.4 times bigger than Earth, respectively, and orbit in their star’s habitable zone — the just-right range of distances that can support liquid water on a planet’s surface.
The five-planet Kepler-62 system lies 1,200 light-years away, making it much too distant for current instruments to study in detail. So any talk of potential life on Kepler-62e and f, if it exists at all, is just speculation for now, Borucki stressed.
But such speculation is hard to resist. For example, Borucki raised the possibility that the newfound “super-Earths” — worlds just slightly bigger than our own planet — could host winged organisms, even if both planets are indeed water worlds.
“At least in our ocean, we have flying fish. They ‘fly’ to get away from predators,” Borucki said.
“So we might find that they have evolved — birds — on this ocean planet,” he added, referring to Kepler-62e.
Water worlds are unlikely to host technologically advanced civilizations like our own, Borucki and other researchers said, because any lifeforms that take root there would not have easy access to electricity or fire for metallurgy.
But if Kepler-62e or f has some dry land, Borucki said, the story could be different. The relatively high gravity of both exoplanets, however, might make the evolution of large bipedal organisms such as humans unlikely.
“We might not have gotten off four legs” if our ancestors had evolved on Kepler-62e or f, Borucki said. Still, the gravity isn’t too oppressive; we’d be able to walk around on Kepler-62f’s surface if transported there today, he added.
We’d have to take some special life-support gear if we made that 1,200-light-year journey. While Kepler-62e is likely hot and muggy all the way up to the polar regions, Kepler-62f orbits a bit farther away from the host star and is probably cooler.
In fact, a thick atmosphere with lots of heat-trapping carbon dioxide may be required to keep Kepler-62f’s surface water liquid. Such an atmosphere would be tough for humans to handle.
“If you want to write a science-fiction story, and you land on both [planets], at least be sure that on f you don’t want to take your mask thingy off,” said modeling-study lead author Lisa Kaltenegger, of the Max Planck Institute for Astronomy and the Harvard-Smithsonian Center for Astrophysics.
Kepler-62e and f are part of a trove of seven newfound planets announced today. Kepler spotted three other planets in the Kepler-62 system as well, all of them too hot to support life. The other two worlds are in the Kepler-69 system, which lies about 2,700 light-years from Earth.
The newly discovered Kepler-69c, which is 1.7 times larger than Earth, may also be capable of supporting life, researchers said.
It is time for the private sector to aid in the search for potentially city-destroying asteroids and meteors, lawmakers said during a hearing Wednesday (April 10).
The House Committee on Science, Space and Technology made the call while hearing from NASA scientists and private-sector asteroid hunters during a hearing entitled “Threats from Space,” with both groups agreeing that something more needs to be done.
“Detecting asteroids should not be the primary mission of NASA,” Rep. Lamar Smith (R-Texas), chairman of the House Committee on Science, Space and Technology, said at the hearing. “No doubt the private sector will play an important role as well. We must better recognize what the private sector can do to aid our efforts to protect the world.” [Meteor Streaks over Russia, Explodes (Photos)]
The meeting Wednesday was the second of three aimed at understanding the threat to Earth posed by asteroids in space. The first hearing took place in late March, and addressed the ways governmental entities, like NASA and the Air Force, are mitigating the risks posed by close-flying space rocks. The meetings were scheduled in response to a surprise meteor explosion over Russia and the close flyby of asteroid 2012 DA14 — both of which occurred on Feb. 15.
Astronomers have mapped the orbits of more than 90 percent of the potentially world-ending asteroids in close proximity to the Earth; however, tracking anything smaller than 0.6 miles (1 kilometer) in diameter is more difficult, said Ed Lu, the CEO of the B612 Foundation, a nonprofit organization in the early stages of building a near-Earth-object-hunting space telescope scheduled for launch in 2018.
“NASA has not even come close to finding and tracking the 1 million smaller asteroids that might only just wipe out a city, or perhaps collapse the world economy if they hit in the wrong place,” Lu said at the hearing.
B612′s space telescope, dubbed Sentinel, will be built to aid in the search for smaller asteroids near Earth. Less than 10 percent of asteroids measuring around 459 feet (140 meters) in diameter have been found, while only 1 percent of all asteroids measuring around 131 feet (40 meters) — or “city killer” range — have been tracked, Lu said.
These city-destroying asteroids are notoriously difficult to track with the ground-based methods used by NASA today because the space rocks are relatively small and dark, said Don Yeomans, the head of NASA’s Near-Earth Object Program.
“A dramatic increase in near-Earth asteroid-discovery efficiencies is achievable using space-based infrared telescopes,” Yeomans said at the hearing.
Searching for space rocks in infrared light — as the $240 million Sentinel is expected to do — could allow astronomers to find a larger number of smaller objects that are too dark to be seen in visible light, Yeomans said.
A space-based asteroid hunter is also helpful because it can seek out space rocks at all hours of the day, as opposed to just at night, Yeomans added.
All of these hunting efforts should be put in place to find near-Earth objects well before they could hit the Earth, the panelists said.
At the moment, we have the technology to deflect an asteroid, but scientists won’t be able to use those methods without ample time to implement them, Michael A’Hearn, an astronomer working with the National Research Council, said at the hearing.
But first, the asteroids have to be found, Lu said.
“You can’t deflect an asteroid that you haven’t yet tracked,” Lu said. “Our technology is useless against something we haven’t yet found.”
NASA’s bold plan to drag an asteroid into orbit around the moon may sound like science fiction, but it’s achievable with current technology, experts say.
President Barack Obama’s 2014 federal budget request, which will be unveiled today (April 10), likely includes about $100 million for NASA to jump-start an asteroid-capture mission, U.S. Senator Bill Nelson (D-FL) said last week.
The plan aims to place a roughly 23-foot-wide (7 meters) space rock into a stable lunar orbit, where astronauts could begin visiting it as soon as 2021 using NASA’s Space Launch System rocket and Orion capsule, Nelson said.
While challenging, the mission is definitely doable, said Chris Lewicki, president and chief engineer of billionaire-backed asteroid-mining firm Planetary Resources. [NASA's Asteroid-Capture Plan (Video)]
“Return of a near-Earth asteroid of this size would require today’s largest launch vehicles and today’s most efficient propulsion systems in order to achieve the mission,” Lewicki, who served as flight director for NASA’s Spirit and Opportunity Mars rovers and surface mission manager for the agency’s Phoenix Mars lander, wrote in a blog post Sunday (April 7).
“Even so, capturing and transporting a small asteroid should be a fairly straightforward affair,” Lewicki added. “Mission cost and complexity are likely on par with missions like the [$2.5 billion] Curiosity Mars rover.”
Spurring solar system exploration
NASA’s idea is similar to one proposed last year by scientists based at Caltech’s Keck Institute for Space Studies in Pasadena.
The Keck study estimated that a robotic spacecraft could drag a 23-foot near-Earth asteroid (NEA) — which would likely weigh about 500 tons — into a high lunar orbit for $2.6 billion. The returns on this initial investment are potentially huge, the researchers said.
“Experience gained via human expeditions to the small returned NEA would transfer directly to follow-on international expeditions beyond the Earth-moon system: to other near-Earth asteroids, [the Mars moons] Phobos and Deimos, Mars and potentially someday to the main asteroid belt,” the Keck team wrote in a feasibility study of their plan.
The mission would also help develop asteroid-mining technology, advocates say, and advance scientists’ understanding of how our solar system took shape more than 4.5 billion years ago.
Asteroids “probably represent samples of the earliest matter that was made available to form our solar system and our Earth,” Caltech’s Paul Dimotakis, a member of the Keck study team, told SPACE.com in February.
“We learned a lot about the moon by analyzing the moon rocks that Apollo astronauts brought back,” he added. [NASA's 17 Apollo Moon Missions in Pictures]
Asteroids are fascinating for lots of reasons. They contain a variety of valuable resources and slam into our planet on a regular basis, occasionally snuffing out most of Earth’s lifeforms. How much do you know about space rocks?
Unmanned probes have successfully rendezvoused with asteroids in deep space multiple times. Japan’s Hayabusa craft even snagged pieces of the near-Earth asteroid Itokawa in 2005, sending them back to our planet for study.
But bagging an entire asteroid and dragging it to our neck of the cosmic woods is unprecedented, and it presents several daunting challenges.
For example, the target asteroid will be spinning, which doesn’t make for a smooth ride to lunar orbit. After the spacecraft captures the asteroid and brings it into a hold of sorts, the space rock will have to be de-spun, likely with thrusters, Dimotakis said.
“You might use reaction jets to take out most of it [the spin],” he said. “You would give you yourself a lot of time to do this, because there’s no second chance in any of this.”
Further, bringing the asteroid onboard greatly increases the spacecraft’s mass, making propulsion and navigation much more difficult. And precise navigation will definitely be required to deliver the space rock to its desired orbit, Dimotakis said (though he also stressed that any asteroid chosen would pose no danger to humanity even if it somehow struck our planet).
But ion thrusters like the ones powering NASA’s Dawn mission to the huge asteroid Vesta and dwarf planet Ceres should be muscular enough to make the journey, likely taking a few years to reach the asteroid and somewhat longer to come back. And the asteroid-laden probe could probably still be guided with great care, he added.
“My guess is that all of these are not insurmountable challenges, and you would be able to calibrate yourself after you snagged it and adjust your controls,” Dimotakis said.
Choosing a target
Perhaps the biggest challenge of the entire mission is picking a suitable space rock to retrieve, Lewicki wrote in his blog post.
The Keck study recommends going after a carbonaceous asteroid packed full of water and other volatiles. Carbonaceous asteroids can be very dark, and it’s tough to spot and characterize a 23-foot asteroid in the vast depths of space whatever its color.
So both Lewicki and Dimotakis stressed the importance of searching for potential asteroid targets sooner rather than later. Planetary Resources plans to begin launching a line of small prospecting space telescopes in 2014 or 2015, and these “Arkyd-100″ craft could aid NASA’s mission, Lewicki wrote.
Dimotakis, for his part, is engaged in a follow-up to the Keck study that’s looking for potential targets in observations made by current telescopes.
“We are developing software in collaboration with JPL [NASA's Jet Propulsion Laboratory] that is going to exploit the observational digital record and essentially flag things that could be of interest and might be in this class,” he said. “This has never happened before.”
Still, mission scientists and engineers shouldn’t just sit on their hands until an asteroid selection is made, he added.
It’s important “to start developing the spacecraft before you even know where you’re going,” Dimotakis said. “If you do these things in parallel, then the mission timeline shrinks.”
Mars is farther away than any near-Earth asteroid that NASA would target, but this disadvantage may be outweighed by the greater knowledge scientists have gained of the Red Planet thanks to the many Mars missions that have launched over the years, experts say.
Further, mapping out an asteroid mission is nearly impossible at this point, since NASA does not yet know where it’s going.
“There are still no good asteroid targets for such a mission, a necessary prerequisite for determining mission length and details such as the astronauts’ exposure to radiation and the consumables required,” states a December 2012 report from the U.S. National Research Council (NRC). [How NASA Will Explore Asteroids (Gallery)]
The road to Mars
Landing astronauts on Mars has been the long-term goal of NASA’s human spaceflight program for decades, but the agency’s vision of how to get there was shaken up recently.
NASA had viewed the moon as a stepping stone, working to get humans to Earth’s natural satellite by 2020 under a program called Constellation, which was initiated during the presidency of George W. Bush. But President Barack Obama cancelled Constellation in 2010, after an independent review panel found it to be significantly under-funded and behind schedule.
instead directed NASA to send astronauts to a near-Earth asteroid by 2025, then on to the vicinity of Mars by the mid-2030s. The agency is developing a new crewed capsule called Orion and a huge rocket called the Space Launch System to make it all happen.
The new “asteroid-next” plan has not been enthusiastically embraced by NASA or the broader space community, the NRC report concluded.
“Despite isolated pockets of support for a human asteroid mission, the committee did not detect broad support for an asteroid mission inside NASA, in the nation as a whole or from the international community,” write the authors of the report, which is called “NASA’s Strategic Direction and the Need for a National Consensus.”
A tough proposition
The NRC report was based on research, interviews, site visits and analysis conducted by a 12-member independent committee over the course of about five months in 2012.
One of the people the study team met with was Bill Gerstenmaier, NASA’s associate administrator for human exploration and operations.
Gerstenmaier “talked about how NASA had discovered, in the two years that had elapsed by the time he was speaking to us, just how hard [a manned asteroid mission] was,” committee member and space policy expert Marcia Smith said during a presentation with NASA’s Future In-Space Operations working group on Jan. 30.
“He said in many respects, it’s easier to go to Mars, because we know a lot about Mars,” Smith added. “We know where it is, and we’ve done all these reconnaissance missions already, so we have a knowledge base from which to work in terms of sending humans, whereas no particular asteroid has been selected yet.”
While sending astronauts to an asteroid has never been done before, unmanned probes have successfully rendezvoused with the objects in deep space multiple times.
For example, NASA’s Dawn spacecraft orbited the protoplanet Vesta — the second-largest body in the main asteroid belt between Mars and Jupiter — for more than a year before departing to head to the belt’s largest denizen, Ceres, last September. And in 2005, Japan’s Hayabusa probe plucked some pieces off the near-Earth asteroid Itokawa, sending them back to Earth for analysis.
NASA plans to launch its own asteroid-sampling mission, called Osiris-Rex, in 2016. And two private companies — Planetary Resources and Deep Space Industries — intend to loft reconnaissance spacecraft over the next few years, kicking off an ambitious efforts to mine water, metals and other resources from asteroids.
Though NASA is devoting many of its exploration resources to Mars these days, the agency still has its eye on an icy moon of Jupiter that may be capable of supporting life as we know it.
Last week, NASA officials announced that they plan to launch a $1.5 billion rover to Mars in 2020, adding to a string of Red Planet missions already on the docket. The Curiosity rover just landed this past August, for example, and an orbiter called Maven and a lander named InSight are slated to blast off in 2013 and 2016, respectively.
But NASA is also thinking about ways to investigate the possible habitability of Europa, Jupiter’s fourth-largest moon. One concept that may be gaining traction is a so-called “clipper” probe that would make multiple flybys of the moon, studying its icy shell and suspected subsurface ocean as it zooms past.
“We briefed [NASA] headquarters on Monday, and they responded very positively,” mission proponent David Senske, of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said here Dec. 7 at the annual fall meeting of the American Geophysical Union. [Photos: Europa, Mysterious Icy Moon of Jupiter]
The $2 billion unmanned Europa Clipper, which could be ready to launch by 2021 or so, would also do vital reconnaissance work for a potential lander mission in the future, Senske told SPACE.com.
Astrobiologists regard Europa, which is about 1,900 miles (3,100 kilometers) wide, as one of the best bets in our solar system to host life beyond Earth.
The moon is believed to harbor a large ocean of liquid water beneath its icy shell. Further, this ocean is likely in direct contact with Europa’s rocky mantle, raising the possibility of all sorts of interesting chemical reactions, Senske said.
The irradiation of Europa’s surface and tidal heating of its interior also mean the moon likely has ample energy sources — another key requirement for life as we know it.
NASA has long been interested in exploring the icy moon and its ocean. Several years back, the agency drew up an ambitious mission concept called the Jupiter Europa Orbiter (JEO), which would have made detailed studies of Europa and the incredibly volcanic Jupiter moon Io.
The science returns from such a mission would have been impressive, according to the 2011 Planetary Science Decadal Survey, which outlined the scientific community’s goals in the field over the coming decade.
The decadal survey ranked JEO as the second-highest priority among large-scale missions, just behind Mars sample-return. But the report said its $4.7 billion price tag was just too high.
“The recommendation was, immediately go and do a de-scope,” said Senske, who was also involved in JEO. “They loved the science; the science was great. But focus it.” [6 Most Likely Places to Find Alien Life in the Solar System]
Paring it down
So researchers got to work developing a leaner, cheaper Europa mission that would fit under a firm $2 billion cost cap. They came up with two main options: the clipper and a Europa orbiter (a lander was ruled out as premature).
Because of the intense radiation environment around Europa, the orbiter would have to be heavily shielded, adding weight and cost. Even with this armor, the concept initially called for a nominal design life at Europa of just 30 days, with later versions boosting that up to 109 days, Senske said.
While the orbiter would gather a great deal of interesting and valuable information, it falls short of what the flyby concept could deliver on a dollar-to-dollar basis, Senske said. For example, a $2 billion orbiter would not be able to carry an instrument that could investigate the composition and chemistry of Europa’s surface and atmosphere (and, by extension, its ocean).
“In terms of an apples-to-apples comparison, Clipper really does rise to the top,” Senske said.
The Europa Clipper
The Clipper would carry a number of scientific instruments, including ice-penetrating radar, a topographical imager, a magnetometer, an infrared spectrometer, a neutral mass spectrometer and a high-gain antenna.
To squeeze all of this gear aboard and still stay under the $2 billion cap, Clipper may need to be powered by solar arrays rather than advanced stirling radioisotope generators as originally envisioned, Senske said. Solar panels are considerably cheaper than ASRGs, which convert the heat from plutonium-238′s radioactive decay into eletricity.
NASA’s Jupiter-bound Juno probe also sports solar arrays, so there is precedent for sending a solar-powered spacecraft so far from the sun. But a Europa mission would present some additional challenges to address, including eclipses and radiation doses about two times higher than Juno will receive.
“We have some things that we need to test,” Senske said.
The Clipper would enter into orbit around Jupiter, then study Europa during dozens of flybys over the course of 2.3 years. On its closest passes, it would come within just 15 miles (25 km) of the moon’s frozen surface.
These close encounters should help the probe crack some of Europa’s most intriguing mysteries, such as the thickness of its ice shell and the saltiness and approximate depth of its ocean (as well as confirming that the ocean exists), Senske said.
This information, along with the spacecraft’s detailed imagery of the moon’s surface, could help guide a potential lander mission that would search for signs of Europan life sometime down the road.
The Clipper could probably be ready to launch between 2020 and 2022, Senske said. Its journey to Europa would take about six years.
The Europa Clipper is not on NASA’s books yet, but agency higher-ups and advisory committees both inside and outside the agency have given it high marks thus far, Senske said.
He and the rest of the team will continue developing the mission concept and see what happens.
“In April, we want to do what we’re calling a preliminary concept review, start working out the bugs, and then working with headquarters to define when we would have what’s known as a mission concept review that would start getting us on the road as a full-up mission,” Senske said.
Some scientists who want close-up studies of potentially habitable moons such as Europa and the Saturn satellite Enceladus were disappointed that NASA selected another Mars rover mission for 2020. But Senske said the agency’s mounting successes at the Red Planet — and the public interest missions such as Curiosity have generated — could eventually make more far-flung exploration efforts possible.
“It could potentially be the tide that raises all ships,” Senske said.
Missions hoping to explore the huge subsurface ocean thought to exist on Jupiter’s moon Europa may have to dig deep — really deep.
Water stays in a liquid state near Europa’s surface for just a few tens of thousands of years or so, new research suggests. That’s a blink of an eye in geological terms, since our solar system is more than 4.5 billion years old.
“A global water ocean may be present, but relatively deep below the surface — around 25 to 50 kilometers,” Klára Kalousová, of France’s University of Nantes and Charles University in Prague, said in a statement today (Sept 24).
“There could be areas of liquid water at much shallower depths, say around 5 kilometers, but these would only exist for a few tens of thousands of years before migrating downwards,” Kalousová added. [Gallery: Photos of Europa]
Many researchers think Europa, which is about 1,900 miles (3,100 km) wide, harbors an enormous global ocean beneath its shell of ice. While Europa’s surface is frigid, heat generated in the moon’s interior by Jupiter’s gravitational pull keeps this ocean — which may be 60 miles (100 km) deep — from freezing solid.
Here on Earth, life thrives wherever liquid water is found. So Europa is an intriguing target for future missions seeking signs of life elsewhere in the solar system.
But scientists don’t know how difficult it would be for a future Europa probe to access the moon’s ocean, because they’re not sure how deep beneath the crust it lies. Some researchers have speculated that pockets of liquid water may persist just a few miles below the surface, but the new study throws cold water on that prospect.
Kalousová mathematically modeled how mixtures of liquid water and solid ice behave in a variety of conditions. She found that differences in density and viscosity, along with several other factors, probably cause water near Europa’s surface to migrate downward rapidly through partially melted ice to meet up with the larger ocean.
Europa isn’t the only moon in the solar system that may have an underground ocean. Fellow Jovian moons Callisto and Ganymede might have one, for example, and so might Saturn’s icy satellite Enceladus.
The new study could help scientists better understand these frigid worlds, as well as Saturn’s huge moon Titan, which has a hydrocarbon-based weather system, Kalousová said.
“As well as helping us to better understand Europa’s water cycle, this research could provide insight into icy moons that are geologically active, such as Enceladus, and worlds that have cycles connecting the interior with a surface atmosphere, such as Titan,” she said.
Kalousová will present the research at the European Planetary Science Congress in Madrid on Tuesday (Sept. 25).
The hunt is on. A group of scientists has banded together to build the world’s first privately funded deep-space telescope, to hunt for asteroids that could pose a major threat to Earth.
The private space telescope forms the heart of Project Sentinel, a deep-space mission being unveiled today (June 28) in Mountain View, Calif., by the B612 Foundation, a nonprofit group of scientists and explorers that has long advocated the exploration of asteroids and better space rock monitoring.
Project Sentinel involves the development of a super-snooper telescope that would be placed in orbit around the sun. The goal, foundation officials say, is to create the first comprehensive dynamic map of our inner solar system.
That map would yield a lively look at the present and future locations and trajectories of near-Earth asteroids, paving the way to protecting the Earth from future impacts and opening the solar system to future exploration. [Sentinel Space Telescope's Asteroid Mission (Pictures)]
An asteroid sentinel in space
Ed Lu is B612 chairman and CEO, a former NASA astronaut who has flown on the space shuttle and Russia’s Soyuz capsule and lived aboard the International Space Station.
“The reason we’re doing this is because we can!”Lu told SPACE.com
Private organizations can now carry out awe-inspiring and audacious projects that previously only governments could accomplish, Lu said.
“So it isn’t crazy to think of a large telescope being funded privately. In fact, historically, that has been the way large, private telescopes here on Earth have been funded. The exception here is that rather than being on the Earth, this one is orbiting the sun,” Lu said.
A lot of work has gone into shaping Project Sentinel over the last year, Lu said. Akin to the architectural plans for a building, he said, a preliminary spacecraft and mission design is complete.
“This isn’t a viewgraph,” Lu added.”What we’ve built is the best technical team on this planet.”
A firm fixed-price proposal to carry out Project Sentinel has been submitted by Ball Aerospace of Boulder, Colo., enabled in part by early infrared-detector work funded by B612.
No stranger to big space scopes, Ball Aerospace is the technical sparkplug behind such NASA-sponsored spacecraft as theplanet-hunting Kepler mission and the infrared Spitzer Space Telescope.
Under a NASA Space Act Agreement signed with B612, the space agency will provide Deep Space Network communications and tracking as well as technical support.
Return To PollHunting asteroids for all mankind
Project Sentinel would complete its near-Earth object (NEO) survey work in 5.5 years.
“The line in the sand is for the spacecraft to find 90 percent of near-Earth objects larger than 140 meters [459 feet] in size. That translates into approximately a 100-megaton explosion should one hit the Earth,” Lu said. “If we go as long as we think we’re going to go, we’re also going to find the vast majority of Tunguskas, too.” [7 Strangest Asteroids in the Solar System]
The Tunguska River in remote Siberia was the site directly under a huge explosion in 1908, an air burst of a large meteoroid or comet fragment estimated to have flattened more than 80 million trees over 830 square miles (2,150 square kilometers).
According to B612, only about 10,000 of the more than half million asteroids larger than the 1908 Tunguska asteroidwhose orbits cross Earth’s orbit have been discovered and tracked.
Project Sentinel would find and road-map Earth-bound asteroids with sufficient warning time – years to decades – to enable deflection missions.
This all adds up to an awe-inspiring project for the global good, the B612 NEO team said.
Space telescope price tag
What’s the cost to build the Project Sentinel telescope?
“We can’t disclose the final price, but I can give you a ballpark of a few hundred million dollars. Which is, I think, a factor of several less than what NASA could do this for,” Lu said.
To foot the bill for Project Sentinel, a worldwide fundraising campaign is being implemented, including outreach to citizens around the globe.
“Our constituency is everybody,” said B612 spokeswoman Diane Murphy.
“If you think about it, what we are is a small capital campaign,” Lu said. “At any given time in the United States, there’s probably a hundred fundraising campaigns larger than this … for symphony halls, museums, performing arts centers.”
Data pipeline set
As now forecast, Project Sentinel would be launched in 2016 aboard a SpaceX Falcon 9 rocket, Lu said. The spacecraft operations center is to be based at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder.
Project Sentinel would require a gravity slingshot off Venus to enter solar orbit. Data relay would be carried out through the NASA Deep Space Network. Data analysis — identification of NEO threats — is to be handled through an existing data pipeline at the Minor Planet Center in Cambridge, Mass., and the NASA Jet Propulsion Laboratory in Pasadena, Calif.
“When you stand back from this, … this is like the whole issue of mapping the U.S, and almost everything else that precedes real development and exploration,” said former astronaut Rusty Schweickart, B612 chairman emeritus, who was the lunar module pilot on the Apollo 9 mission.
“The meta-view of what we’re doing … is mapping the Earth, sun, the inner solar system … the Earth Territory, if you will,” Schweickart said. That, he said, would pave the way toward protecting the Earth from impacts and opening the solar system to exploration.
Legacy space systems
“An exciting aspect of Ball’s role on Sentinel is leveraging sophisticated technology developed under the Deep Impact, Spitzer, and Kepler missions for the B612 Foundation,” said John Troeltzsch, the company’s Sentinel Program manager.
Troeltzsch told SPACE.com the aerospace firm will reuse deep-space elements the company helped pioneer. For the privately funded mission, that could include the science-downlink technology flown on Kepler and the cryogenic thermal-isolation system from the Spitzer Space Telescope.
The Sentinel ground system will build on the system in daily use by the Kepler mission, which is supplied to Ball by the LASP at Colorado-Boulder.
“Ball has been working on the mission concept for a NEO survey mission like Sentinel since 2005. This has allowed us to refine and iterate the design to a state of maturity that supports a commercial offering to B612,” Troeltzsch said. “Although there are challenges in front of us, like the development of the focal plane detectors, the overall system is based on proven, high-heritage systems.”
Troeltzsch said it’s not every day you can have fun working on a powerful space telescope and help protect the planet at the same time.
“Sooner or later one of the NEOs that Sentinel will discover will end up on a collision course with the Earth. I am sure that my kids and grandkids will appreciate the foresight B612 has shown in sponsoring this mission to help protect us all,” Troeltzsch concluded.
Big, bad Jupiter likely squashed any chance the giant asteroid Vesta may have had of growing into a full-fledged planet long ago, researchers say.
Scientists analyzing observations from NASA’s Dawn spacecraft announced on (May 10) that the enormous asteroid Vesta is actually an ancient protoplanet, a planetary building block left over from the solar system’s earliest days.
Many other Vesta-like objects were incorporated into rocky worlds such as Earth, but Vesta’s development along this path was halted.
Vesta’s stunted growth is chiefly a product of its location, researchers said. The protoplanets that glommed together to form Mercury, Earth, Mars and Venus did so in the inner solar system, relatively far from the disruptive gravitational influence of a giant planet.
The 330-mile-wide (530-kilometer) Vesta, on the other hand, grew up in the main asteroid belt between Mars and Jupiter. And the solar system’s largest planet made it tough for Vesta to hook up with others of its kind.
“In the asteroid belt, Jupiter basically stirred things up so much that they weren’t able to easily accrete with one another,” Dawn scientist David O’Brien, of the Planetary Science Institute in Tucson, Ariz., told reporters today.
“The velocities in the asteroid belt were really high, and the higher the velocity is, the harder it is for things to merge together under their own gravity,” O’Brien added.
Those high velocities also set the stage for some incredibly violent collisions, which probably destroyed a fair number of Vesta-like bodies. Vesta itself was battered and bloodied by some huge impacts; one crater near its south pole is 314 miles (505 km) wide, and another underneath that one measures 250 miles (400 km) across.
So while Vesta — the second-largest denizen of the asteroid belt — was doomed to a life of solitude, it has had the toughness and luck to stick around for the last 4.5 billion years. And scientists are thankful that it did.
“Vesta is special, because it survived the intense collisional environment of the main asteroid belt for billions of years, allowing us to interrogate a key witness to the events at the very beginning of the solar system,” said Dawn deputy principal investigator Carol Raymond, of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“We believe Vesta is the only intact member of a family of similar bodies that have since perished,” she added.
Science fiction dreams of mining riches from asteroids only make sense if humans can make it worth their time and effort. The new Planetary Resources group backed by Silicon Valley billionaires and Hollywood moguls is now betting on the fact that there is big money in mining space rocks.
Nobody knows exactly how much asteroid wealth exists, but early estimates point to riches beyond Earth’s wildest dreams. Just the mineral wealth of the asteroid belt between the orbits of Mars and Jupiter could be equivalent to about $100 billion for every person on Earth, according to “Mining the Sky: Untold Riches from the Asteroid, Comets, and Planets” (Addison-Wesley, 1996) — perhaps slightly less now after accounting for the Earth’s population growth over the past 15 years. [Does Asteroid Mining Violate Space Law?]
“The near-Earth asteroid population could easily support 10 to 40 times the population of Earth, with all the necessary resources to do that,” said John Lewis, a professor emeritus at the Lunar and Planetary Laboratory of the University of Arizona and author of “Mining the Sky.”
Even smaller space rocks can have mineral prizes worth tens of trillions of dollars. The smallest known metallic asteroid that is an accessible near-Earth object has 40 times as much metal as all the metal in Earth’s history, Lewis pointed out. He has joined Planetary Resources as perhaps the most recognized expert on asteroid wealth.
There’s platinum in thar rocks
Knowing what asteroid wealth consists of depends on incomplete but enticing scientific surveys. Scientists sitting on Earth can detect chemical signatures of asteroids based on reflected light, or directly sample space rocks fallen to Earth as meteoroids. Japan has carried out the only successful space mission to retrieve asteroid samples in space, but the U.S. is planning its own asteroid sample and retrieval missions.
An M-class asteroid about 79-feet (24-meter) long could have as much as 33,000 tons of extractable metal and possibly one ton of platinum group metals. The platinum alone could be easily worth about $50 million dollars in Earth’s commodity markets, according to studies cited by the paper “Assessment on the feasibility of future shepherding of asteroid resources” in the April-May issue of the journal Acta Astronautica.
Such platinum-group metals represent the main prize for Earth markets, said Joan-Pau Sanchez, a researcher in the Advanced Space Concepts Laboratory at the University of Strathclyde in the UK. He coauthored the Acta Astronautica paper.
“Platinum-group metals (PGMs) are likely to be the only material from asteroids that will prove economically viable to be transported back to Earth’s commodity markets,” Sanchez told InnovationnewsDaily. “PGMs are in high demand, and will be even more in the future.”
Turning space rocks into riches
But the Planetary Resources group has its eyes on more than just platinum to strike it rich, Lewis said. He described using asteroid metals to build huge space stations or even space solar power stations for beaming energy down to Earth.
That could come from the abundant S-class asteroids — about 40 percent of the near-Earth objects — which hold metals, semiconductors, and even oxygen or water. One 79-foot (24-meter) asteroid of the S-class could provide 1,100 to 4,400 tons of iron for building the structural support for a huge solar array capable of making a gigawatt of power (as much as a large power plant) for either space stations or Earth, according to the Acta Astronautica paper.
A similar-size hydrated carbonaceous asteroid could hold a million liters of water (enough to fill half a million soft drink bottles). That would fall under the second big market envisioned by Planetary Resources — harvesting asteroid resources for use as rocket propellants, drinking water and oxygen to support space exploration missions.
“The billionaires who are standing behind this right now are not doing this for fun and recreation,” Lewis said. “They see it as a great economic value in the long run, and I’m not surprised if more than one wants to make a dime out of it.”
Considered one of the best potential sources for extraterrestrial life in the solar system, Jupiter’s moon Europa may host life in the ocean deep beneath the moon’s icy crust.
Some organisms could even travel to Europa’s surface through cracks and instabilities in the crust, some researchers speculate. But radiation from Jupiter’s magnetosphere constantly bombards the moon and could annihilate life at shallow depths, making it difficult to detect with an orbiter or lander.
So scientists are seeking to determine experimentally just how deep organic life on Europa needs to hide in order to avoid being destroyed.
Jupiter’s magnetosphere blasts Europa — which is slightly smaller than Earth’s moon — with high-energy electrons in the megaelectron volt (MeV) range. But most of the scientific data on how high-energy radiation affects organics has focused on the medical field, where studies seek to determine how chemotherapy affects the human body. That research focuses on water, the body’s primary component.
“Simple theories of how deep the electrons go are only known for very high-energy electrons,” said Murthy Gudipati, of NASA’s Jet Propulsion Laboratory, which is managed by the California Institute of Technology in Pasadena. Gudipati’s research focuses on electrons bombarding ice instead. [Photos: Europa, Mysterious Icy Moon of Jupiter]
“Even in the megaelectron volt range, we do not have any laboratory data that has been measured on ices containing organic matter, which is really important for astrobiology,” Gudipati said.
The power of electrons
Gudipati and his team placed organic detector molecules behind ice of varying thickness, then fired an electron gun at them. They measured not only how deeply the electrons themselves traveled, but also the penetration of the photons knocked loose by the electrons — a secondary effect that other experiments have not tracked.
“Those photons can penetrate far deeper and cause damage to organic matter,” Gudipati said.
The process is akin to placing a person behind a wall and speaking at different frequencies while changing the thickness of the barrier, he added. Except, of course, the frequencies studied here can kill organic molecules rather than converse with them.
Wes Patterson, a planetary scientist at Johns Hopkins University, compared the effects of Jupiter’s radiation to the doses people can get during a visit to the hospital.
“There’s a reason why lab techs wear lead vests when giving X-rays,” Patterson said. “Exposure over a short time may not do too much to you, but if you’re constantly exposed to radiation, it will harm the body.”
He reiterated the importance of the research’s experimentation with ice rather than water calling it “a vital first step.”
Step by step
The team focused on low-energy electron radiation, up to ten thousand times less than the intense barrage pumped out by Jupiter. In this lower range, the depth to which the electrons penetrate is directly related to the strength of the radiation.
The researchers considered three scenarios as the bombardment increases in strength. Two take into account potential changes that may come with depth; at stronger energies, the electrons could do more or less damage, which the team has calculated. However, if the results remain the same at higher energy levels, radiation of 100 MeV will penetrate between 60 to 80 centimeters (23 to 32 inches).
This may not sound like it would be a problem, but if a lander sent to Europa digs only 2 feet (0.6 meters) into a highly irradiated area of the crust in search of life, it most likely wouldn’t find any because electrons likely would have destroyed any organics in that region. [Touring Jupiter's Big Moons: Io, Ganymede, Europa, Callisto]
The team plans to extend the study on the effects of increased radiation energy incrementally. One reason for the gradual extension is because not all of Europa experiences the same exposure.
Jupiter’s magnetosphere rotates with the planet, about every ten hours, while it takes 85 hours for Europa to orbit Jupiter. Consequently, the magnetosphere constantly overtakes the moon, exposing the back side, or trailing hemisphere, to more radiation than the front. The equatorial region of the trailing side suffers more damage than its poles.
“We need to understand how that depth varies with location,” Patterson said.
That’s something Gudipati hopes to achieve.
“We need to do step-by-step lab studies covering as much of the region as possible that is pertinent for Europa,” he said.
Eventually, he hopes to run experiments at energy ranges comparable to Jupiter’s magnetic field, though he noted that each step will grow more expensive. But when it comes to preparing a mission to Europa, the cost of insufficient knowledge could be higher.
“If we are investing millions or billions [in a mission to Europa], then it is worth investing half a million to a million dollars to get this full range covered,” Gudipati said.
Patterson agreed. “This looks like a really great start on something that would be important for future consideration for landing on Europa, and even for trying to understand what we could observe from orbit.”
Such experiments could help create realistic goals for potential missions to Europa. Without them, finding organic molecules on the icy moon could be far more challenging, researchers said.
“If we do not know how deep to dig through lab simulations, we will be tossing a coin,” Gudipati said.
The universe is filled with high-energy radiation, much of which is made of gamma rays belched out by strange pulsing stars and the remnants of supernova explosions. But a new study of some of most extreme objects has turned up a mystery: nearly one-third of all gamma-ray emitting objects seen to date defy identification.
The objects were spotted by NASA’s Fermi Gamma-ray Space Telescope, which scans the entire sky over the course of three hours, mapping the powerful spectrum. When stacked together, the surveys create an extremely precise view of the gamma-ray universe.
Scientists then match these images to other observations to identify each source. But the identities of some gamma-ray sources in space still continue to elude the astronomers.
“There’s some that, despite all our efforts, we really do not know what they are,” David Thompson, Fermi’s deputy project scientist, told SPACE.com. “They do not seem to be any of the usual suspects.” [Video: Mystery of Fermi's Gamma-Ray Objects]
The cosmic detective
The Fermi space telescope has spotted nearly 500 powerful gamma-ray sources in deep space over the last three years. Before its launch in 2008, scientists only knew of four such objects.
“We’re not looking for the ordinary things,” Thompson said. “We’re looking for the extraordinary; powerful things that might produce gamma rays.”
Of the newly discovered bodies, more than half are active galaxies. Pulsars and supernova remnants each make up about 5 percent of the sources, with high-mass binary stars and other galaxies contributing just a smidge more, the researchers said.
Yet a large collection of objects remains unidentified, they added.
In some cases, the readings themselves helped scientists to classify the sources. By looking for changes in energy levels or studying the objects’ shapes, astronomers could identify pulsars and galaxies.
But gamma-ray targets without these distinctions remain a mystery. In many cases, the problem may simply be one of not enough data.
“Deeper observations at other wavelengths could find counterparts to some Fermi sources in the future,” Pascal Fortin, at the Ecole Polytechnique’s Laboratoire Leprince-Ringuet in France, told SPACE.com in an email. Fortin was one of the leaders of the international team that produced Fermi’s hard-source list.
A tantalizing mystery
Despite their mysterious origins, the sheer number of unidentified sources is promising.
“The fact that there are so many of these suggests to us — maybe this is wishful thinking — that there may indeed be something new out there,” Thompson said. “What we’d really like to find is something new and exotic.”
One potential cause of the baffling readings could be black holes that are interacting in a new and unexpected way, he added.
If the strange objects reveal nothing else, they highlight how much of space is still a mystery.
“We still have a lot to learn about high-energy processes in the universe,” Fortin said.
Over its decade-long mission, Fermi will continue to gather information about the gamma-ray emitters, and may help answer some of the questions it is creating.
“It’s an exciting field to work in,” Thompson said. “The fact that we have so many of these, I think is very promising in terms of future discoveries.”
A NASA spacecraft orbiting the huge asteroid Vesta has snapped amazing new photos of the colossal space rock, images that reveal strange features never-before-seen on an asteroid, scientists say.
The new photos of Vesta from NASA’s Dawn spacecraft highlight odd, shiny spots that are nearly twice as bright as other parts of the asteroid — suggesting it is original material left over from the space rock’s birth 4 billion years ago, NASA officials said today (March 21).
With a width of about 330 miles (530 km), asteroid Vesta is one of the largest and brightest objects in the main asteroid belt between the orbits of Mars and Jupiter. NASA’s Dawn probe has been orbiting Vesta since 2011 to study the space rock in unprecedented detail.
“Our analysis finds this bright material originates from Vesta and has undergone little change since the formation of Vesta over 4 billion years ago,” said Jian-Yang Li, a Dawn participating scientist at the University of Maryland, College Park, in a statement. “We’re eager to learn more about what minerals make up this material and how the present Vesta surface came to be.”
Asteroid Vesta unveiled
Li and his colleagues unveiled Dawn’s new views of Vesta today at the 43rd Lunar and Planetary Science Conference in The Woodlands, Texas.
The photos show surprisingly bright spots all over Vesta, with the most predominant ones located inside or around the asteroid’s many craters. The bright areas range from large spots (around several hundred feet across) to simply huge, with some stretching across 10 miles (16 kilometers) of terrain. [Video: Vesta — Asteroid or Dwarf Planet?]
“Dawn’s ambitious exploration of Vesta has been going beautifully,” said Marc Rayman, Dawn chief engineer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., which oversees the mission. “As we continue to gather a bounty of data, it is thrilling to reveal fascinating alien landscapes.”
Dawn mission scientists suspect the bright patches on Vesta were exposed during violent collisions with other space rocks. These impacts may have spread the bright material across the asteroid and mixed it together with darker material on Vesta’s surface, researchers said.
Astronomers have known about variations in Vesta’s brightness for some time. Photos taken by the Hubble Space Telescope before Dawn arrived at the asteroid also revealed the bright patches.
Never-before seen asteroid melt
But only the close-up photos from the Dawn probe have revealed the surprising variety of dark blotches on Vesta, which appear as dark gray, brown or reddish blemishes, NASA officials said.
In some views, these darker spots are small deposits near impact craters, while in other photos they appear in larger concentrations. These darker spots on Vesta may also be the result of collisions on the asteroid, researchers said.
Slow carbon-rich asteroids may have created some of the smaller dark material deposits without carving out a big crater. Meanwhile, faster objects may have potentially slammed into Vesta so hard they melted the big asteroid’s crust, which could have also created the dark spots.
“Some of these past collisions were so intense they melted the surface,” said Brett Denevi, a Dawn participating scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “Dawn’s ability to image the melt marks a unique find. Melting events like these were suspected, but never before seen on an asteroid.”
NASA launched the $466 million Dawn spacecraft in 2007 and Vesta is only the first stop of the spacecraft’s two-asteroid tour. Dawn arrived at Vesta in July 2011 and is expected to spend about a year there before heading off to its next target — the even larger asteroid Ceres, which is also classified as a dwarf planet.
Dawn is expected to arrive at Ceres in February 2015.