Mercury is the closest planet to the sun. But although it boasts the most widely varying temperatures in the solar system, it is not the hottest planet How is this possible?
Orbiting between 28 and 43 million miles (46 and 70 million kilometers) from the sun, Mercury, also the smallest planet, feels the brunt of the solar rays. According to NASA, the tiny world suffers the most extreme temperature range of any other planet in the solar system. The day side of the planet reaches temperatures of up to 800 degrees Fahrenheit (427 degrees Celsius). In contrast, the chilly night side can get as cold as minus 290 F (minus 180 C). The planet has an average temperature of 332 F (167 C).
These variations are relatively long-lived. Scientists once thought that Mercury kept a single side perpetually facing the sun, in a condition known as tidal locking. Because the planet lies so close to the sun, it could only be studied when it showed the same rocky, cratered face toward Earth, though at different points in its orbit. However, further studies revealed that the planet spins very slowly — only three times every two Mercury years, or once every 60 Earth days.
Mercury’s low mass and proximity to the sun keep it from having anything but the thinnest of atmospheres, and this is the reason it must pass on being the hottest planet. An atmosphere helps to cloak a planet, keeping heat from leaking into space. Without an atmosphere, Mercury loses a great deal of heat into space, rather than sharing with its night side.
The hottest planet, incidentally, is Venus, the second body from the sun. Venus has a thick atmosphere that blankets the planet, keeping its temperature at an average of 864 F (462 C).
On Earth, seasonal temperature shifts are caused by the tilt of the planet’s axis. If the Southern Hemisphere is closer to the sun than its northern counterpart, it experiences spring and summer instead of autumn and winter. But on Mercury, the planet has essentially no tilt, which means that the hemispheres experience no significant difference in temperature from one another.
That allows Mercury, the closest planet to the sun, to hang onto ice at its surface. Parts of the poles never see sunlight, leading scientists to hypothesize that ice could survive on the world. Observations made from Earth in 1991 identified unusually bright patches that corresponded with craters mapped by Mariner 10 in the 1970s. When NASA’s MESSENGER spacecraft studied the north pole in 2011, it confirmed that radar-bright features at the poles were consistent with shadowed regions. In 2012, MESSENGER used a technique known as neutron spectroscopy to measure the average hydrogen concentrations in the radar-bright regions, strengthening the case for water.
“The neutron data indicates that Mercury’s radar-bright polar deposits contain, on average, a hydrogen-rich layer more than tens of centimeters thick beneath a surficial layer 10 to 20 centimeters thick that is less rich in hydrogen,” said MESSENGER participating scientist David Lawrence at the Johns Hopkins University Applied Physics Laboratory. “The buried layer has a hydrogen content consistent with nearly pure water ice.”
After the discovery, MESSENGER continued to study the polar ice deposits over its extended mission. By refining the imaging, MESSENGER captured images of the deposits on the surface.
“There is a lot to be learned by seeing the deposits,” Nancy Chabot, instrument scientist for MESSENGER’s Mercury Dual Imaging System, said in a statement.
However, Mercury has the least circular, most eccentric orbit of all the planets. The huge range in its distance from the sun means that the planet does feel some variation in temperature based on where it travels over the course of its 88 Earth-day year.
During its wheeled treks on the Red Planet, NASA’s Spirit rover may have encountered a potential signature of past life on Mars, report scientists at Arizona State University (ASU).
To help make their case, the researchers have contrasted Spirit’s study of “Home Plate” — a plateau of layered rocks that the robot explored during the early part of its third year on Mars — with features found within active hot spring/geyser discharge channels at a site in northern Chile called El Tatio.
The work has resulted in a provocative paper: “Silica deposits on Mars with features resembling hot spring biosignatures at El Tatio in Chile.”
As reported online last week in the journal Nature Communications, field work in Chile by the ASU team — Steven Ruff and Jack Farmer of the university’s School of Earth and Space Exploration — shows that the nodular and digitate silica structures at El Tatio that most closely resemble those on Mars include complex sedimentary structures produced by a combination of biotic and abiotic processes.
“Although fully abiotic processes are not ruled out for the Martian silica structures, they satisfy an a priori definition of potential biosignatures,” the researchers wrote in the study.
Spiritlanded on Mars in January 2004, a few weeks before its twin, Opportunity, touched down in a different part of the Red Planet. Both golf-cart-size rovers were tasked with looking for signs of past water activity during their missions, which were originally planned to last three months.
Spirit encountered outcrops and regolith composed of opaline silica (amorphous SiO2nH2O) in an ancient volcanic hydrothermal setting in Gusev crater.
An origin via either fumarole-related acid-sulfate leaching or precipitation from hot spring fluids was considered possible. “However, the potential significance of the characteristic nodular and [millimeter]-scale digitate opaline silica structures was not recognized,” Ruff and Farmer noted in the new study.
Spirit imagery shows opaline silica nodular outcrops adjacent to Home Plate showing typical stratiform expression. White outline highlights nodular silica outcrop. Rover wheel tracks are roughly 1 meter apart. Rolling wheels did not deform the roughly 6-inch-high high outcrop (lighter tracks) compared with the inoperative dragging wheel in a later traverse (darker track).
Credit: ASU/Ruff & Farmer
El Tatio: Mars-like conditions
The physical environment of El Tatio offers a rare combination of high elevation, low precipitation rate, high mean annual evaporation rate, common diurnal freeze-thaw and extremely high ultraviolet irradiance.
“Such conditions provide a better environmental analog for Mars than those of Yellowstone National Park (USA) and other well-known geothermal sites on Earth,” suggested Ruff and Farmer. “Our results demonstrate that the more Mars-like conditions of El Tatio produce unique deposits, including biomediated silica structures, with characteristics that compare favorably with the Home Plate silica outcrops. The similarities raise the possibility that the Martian silica structures formed in a comparable manner.”
Previously, a NASA science team defined a potential biosignature as “an object, substance and/or pattern that might have a biological origin and thus compels investigators to gather more data before reaching a conclusion as to the presence or absence of life.”
“Because we can neither prove nor disprove a biological origin for the microstromatolite-like digitate silica structures at Home Plate, they constitute a potential biosignature according to this definition,” Ruff and Farmer wrote.
Spirit bogged down on Mars in May 2009, becoming stuck in soft soil.
In late January 2010, after months of attempts to free the rover, NASA dubbed the wheeled robot a stationary research platform. The lack of mobility and the harsh climes of Mars conspired to seal Spirit’s fate, with attempts to regain contact with the robot ending in May 2011. Subsequently, NASA announced the end of contact efforts and the completion of Spirit’s mission. (Opportunity is still going strong today.)
The ASU researchers suggested that a future and specially instrumented rover mission could perhaps provide a more definitive assessment of possible biogenicity of Home Plate silica structures.
“However, because of the challenges in obtaining unambiguous evidence in situ, coordinated microscopic and compositional analyses of samples returned to laboratories on Earth may be required to reach a robust conclusion as to the presence or absence of past Martian life in these rocks,” Ruff and Farmer stated.
The new study can be viewed here: http://www.nature.com/articles/ncomms13554
Leonard David is author of “Mars: Our Future on the Red Planet.” The book is a companion to the National Geographic Channel six-part series airing in November. A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us @Spacedotcom, Facebookor Google+. Story published on Space.com.
Poor little Mercury is getting even smaller.
Astronomers have discovered a large valley on Mercury that provides further evidence for the planet’s shrinkage — an odd phenomenon that has been the topic of debate for decades.
This newfound feature is about 620 miles long, 250 miles wide and 2 miles deep (1,000 by 400 by 3.2 kilometers), making it larger than Arizona’s famous Grand Canyon and deeper than the Great Rift Valley in East Africa, scientists said.
Unlike Earth’s Great Rift Valley, Mercury’s great valley is not caused by the pulling apart of lithospheric plates due to plate tectonics; it is the result of the global contraction of a shrinking one-plate planet,” Tom Watters, a senior scientist at the Smithsonian National Air and Space Museum in Washington, D.C., said in a statement.
Using colorized topography, Mercury’s “great valley” (dark blue) and Rembrandt impact basin (purple, upper right) are revealed in this high-resolution digital elevation model merged with an image mosaic obtained by NASA’s MESSENGER spacecraft.
Watters is lead author of a study published in Geophysical Research Letters that describes Mercury’s great valley. He and his colleagues spotted the feature in images captured by NASA’s MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft, which orbited the planet from March 2011 through April 2015.
Mercury is 3,032 miles (4,880 km) wide, and the vast majority of the planet’s volume is taken up by its metallic core, which is estimated to be about 2,500 (4,000 km) wide. That core has been cooling slowly since Mercury (and the other planets) formed nearly 4.6 billion years ago, and the little world has been shrinking as a result.
The aforementioned debate involves the extent of that shrinkage. Observations by NASA’s Mariner 10 spacecraft, which flew by Mercury three times in the mid-1970s, suggested that the planet has contracted by 1.2 to 2.5 miles (2 to 4 km) since its formation — significantly less than researchers’ models had predicted.
But MESSENGER got a better look at Mercury, and its meticulous work allowed scientists to up the shrinkage estimate to 8.7 miles (14 km) or so. This higher number reconciled theory with observation
As Watters noted, Mercury’s crust is composed of a single plate (unlike Earth’s, which consists primarily of seven large, interlocking plates). As Mercury has cooled, the rocks in this plate have been pushed together, thrusting some of them upward in cliff-like formations called scarps.
Two large, parallel scarps bound Mercury’s great valley. But the valley’s floor lies below the surrounding terrain, suggesting that the valley also formed via another process called “long-wavelength buckling,” NASA officials said. Basically, the valley floor sagged downward as nearby rocks were pushed up.
“There are similar examples of this on Earth involving both oceanic and continental plates, but this may be the first evidence of this geological process on Mercury,” Watters said.
The Parkes dish becomes the third telescope to be employed by Breakthrough Listen, joining the Green Bank Telescope in West Virginia and the Automated Planet Finder at Lick Observatory in Northern California.
“The addition of Parkes is an important milestone,” billionaire entrepreneur Yuri Milner, founder of the Breakthrough Initiatives, which include Breakthrough Listen, said in a statement. “These major instruments are the ears of planet Earth, and now they are listening for signs of other civilizations.”
The first Breakthrough Listen observations for the Parkes dish came Monday, when scientists turned the telescope toward the Proxima Centauri star system to look for possible signals from alien civilizations
Proxima Centauri is the closest star to the sun, lying just 4.2 light-years away from Earth’s star. This past August, astronomers announced the discovery of an Earth-size planet orbiting in Proxima Centauri’s “habitable zone,” the just-right range of distances where liquid water could exist on a world’s surface.
It’s therefore possible that the planet, known as Proxima b, may be capable of supporting life as we know it, scientists have said.
“The chances of any particular planet hosting intelligent life-forms are probably minuscule,” Andrew Siemion, director of the University of California, Berkeley’s SETI (Search for Extraterrestrial Intelligence) Research Center, said in the same statement.
“But once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes,” Siemion added. “To find a civilization just 4.2 light-years away would change everything.”
Proxima Centauri is also the target of Breakthrough Starshot, a Breakthrough Initiatives effort that aims to blast tiny, sail-equipped “nanoprobes” toward the system at 20 percent the speed of light using powerful lasers.
Milner and a group of researchers, including famed cosmologist Stephen Hawking, announced Breakthrough Listen in July 2015. Over the next 10 years, the $100 million endeavor aims to search the 1 million stars closest to the sun, as well as the 100 nearest galaxies to the Milky Way, for possible SETI signals.
The 210-foot-wide (64 meters) Parkes dish, which is operated by Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO), lies near the town of Parkes, in the state of New South Wales. The radio telescope famously helped relay live video of the Apollo 11 moon landing back to Earth in July 1969, a role featured in the 2000 film “The Dish.”
Breakthrough Listen representatives also announced last month that the project would be teaming up with China’s new Five-hundred-meter Aperture Spherical radio Telescope (FAST) — the world’s largest radio telescope — to coordinate SETI observations.
Single-celled microbes are considered a living example of the kind of life that might exist elsewhere in the universe, as they are able to survive some of the extreme conditions that exist on other worlds.
New research on the bacterium Tepidibacillus decaturensis shows that it could be a model organism for what might live on Mars, should any creature inhabit the Red Planet. This microorganism, found in water more than a mile underground in the Illinois Basin in a formation known as Mount Simon Sandstone, has been shown to be moderately tolerant of heat and salt and able to persist in an anoxic environment. Mars itself is believed to harbor similarly briny surface water without the presence of oxygen.
A paper based on this research, entitled “Tepidibacillus decaturensissp. nov.: a microaerophilic, moderately thermophilic iron-reducing bacterium isolated from a depth of 1.7 km in the Illinois Basin, USA,” was published in the International Journal of Systematic and Evolutionary Microbiology. [The Life on Mars Search: Photo Timeline]
The research was led by Yiran Dong, a research scientist at the Carl R. Woese Institute of Genomic Biology, Robert Sanford, a geomicrobiologist and research associate professor at the University of Illinois, Urbana-Champaign, and Bruce W. Fouke, a professor at the University of Illinois, Urbana-Champaign and was co-funded by the NASA Astrobiology Institute and the National Energy Technology Laboratory.
The research team piggybacked on drilling activity completed by the Midwest Geological Sequestration Consortium (MGSC), which includes the Illinois State Geological Survey (ISGS) and Archer Daniels Midland (ADM). Supported by the Department of Energy, this project is evaluating locations for storing carbon underground to sequester the enormous volume of CO2 emissions being produced by ADM industrial food production, Sanford explained.
The research team participated in two drill sessions that were completed on the grounds of the ADM facility in Decatur, Illinois. Both wells are within 1,000 feet of one another and clean deep, subsurface groundwater was collected at a variety of depths. The target lithology of the Mount Simon sandstone in this central portion of the Illinois Basin ranges from 1.5 kilometers (0.93 miles) to 2.2 kilometers (1.4 miles) in burial depth. This habitat also happens to have iron oxide minerals coating the sandstone grains, which is also true of much of the surface of Mars.
“There have been some iron-reducers [bacteria] found at deep subsurface environments,” Sanford said. “These organisms have respiratory functions for reducing iron; they are reducing iron like we use oxygen. They use ferric iron to breathe.”
The bacterium they were studying, however, is a fermentative organism. Another example of this kind of organism is yeast, a fungus that converts sugar to alcohol through enzymes. Tepidibacillus decaturensis does not use iron to breathe, but it uses iron to sustain its metabolism in a very similar fashion to how yeast produce ethanol to sustain theirs.
The team is analyzing the genomic composition of Tepidibacillus decaturensis. Luckily, they have found another, separate iron-reducing bacterium from the same geological formation called Orenia metallireducens, the first known bacterial species in genus Orenia that reduces ferric to ferrous iron. (A study based on this finding was recently accepted in the journal Applied and Environmental Microbiology.)
The combination of these two iron-reducing bacteria will allow the scientists to conduct comparative studies of their metabolisms and ecology, permitting them to further explore these novel metal-reducing mechanisms. Two iron-dependent organisms in a similar environment provide valuable comparisons to understand how life behaves in these deep, hostile environments.
In previous work published in the journal Genome Announcements earlier in 2016, the team presented the first sequenced genome of Tepidibacillus decaturensis. They found nearly 3,000 protein-coding genes and 52 transfer RNA (tRNA) genes; tRNA is used to decode messenger RNA sequences into proteins.
“We are trying to see whether there are some new [gene] features to set up experiments to test them, and thus explore for the first time the deep evolutionary history of these organisms on Earth and potentially Mars,” Dong said of the ongoing work.
As with everything in life, too much of a good thing can be bad — and that logic now seems to apply to alien life, too.
Since Proxima Centauri b (or just Proxima b) was discovered in August, countless imaginings as to what the small, Earth-sized planet would look like up-close have captivated the media. Is the planet truly Earth-like with mountains, oceans, lush green continents and an atmosphere in just the right proportions to support extraterrestrial life? Or is it actually a dry, barren hellhole being constantly irradiated by its star? It could go either way.
As Proxima b was only detected by its gravitational influence on Proxima Centauri — the small exoplanet’s orbit causes the tiny star to wobble — we only know its mass and orbital period. But these two characteristics are exciting. Not only is Proxima b of approximate Earth-mass, it also orbits within the star’s habitable zone, the region surrounding a star that is neither too hot or too cold for liquid water to exist on the surface.
On Earth, where there’s liquid water, there’s life. So if Proxima b has water on its surface, it might also be in a liquid state, so there’s certainly some excitement surrounding the possibility that the world may also play host to life. But so far, we have absolutely zero evidence that water is even there, so its life-giving potential is purely speculative.
Now, in new research by astrophysicists at the University of Bern, they’ve tackled this problem with planetary evolution models and found that red dwarf stars may preferentially host small, rocky worlds. Not only that, these worlds would likely contain large quantities of water.
“Our models succeed in reproducing planets that are similar in terms of mass and period to the ones observed recently,” said Yann Alibert, of the Center of Space and Habitability (CSH) at the University of Bern, in a statement. “Interestingly, we find that planets in close-in orbits around these type of stars are of small sizes. Typically, they range between 0.5 and 1.5 Earth radii with a peak at about 1.0 Earth radius. Future discoveries will tell if we are correct!”
From this study, which has been accepted for publication in the journal Astronomy & Astrophysics, these small alien worlds also evolved with huge quantities of water. For 90 percent of the exoplanets simulated, their total mass consisted of over 10 percent water. Considering Earth is only 0.02 percent water, the simulated red dwarf exoplanets are veritable ocean planets!
At first glance, this might seem like an incredible opportunity for advanced life forms to evolve on planets in red dwarf systems. After all, red dwarfs are among the most ancient of stars in our galaxy and have a predicted lifespan of longer than the age of the universe (14 billion years). Life on Earth only sprung into being 3 billion years ago when our sun was young; life on red dwarf worlds could evolve over epic timescales by comparison.
And now it seems that, according to established planetary formation theories, these ancient worlds could have a plentiful supply of water? Well, the mind boggles.
But a huge supply of water on small exoplanets orbiting red dwarfs may not necessarily be a good thing. “While liquid water is generally thought to be an essential ingredient, too much of a good thing may be bad,” said study co-author Willy Benz.
In previous studies, water-dominated worlds were found to have unstable climates that may work against the evolution of life, perhaps stymieing these planets’ potential for producing complex life forms. If this is the case, super-advanced alien civilizations stand little chance of becoming a reality. Add this to the fact that any habitable zone exoplanets around red dwarfs will be so close to their stars that they are constantly bathed in huge doses of radiation. Perhaps the only possible life on these worlds will be basic aquatic life and have to exist deep under protective layers of icy crust.
“Habitable or not, the study of planets orbiting very low mass stars will likely bring exciting new results, improving our knowledge of planet formation, evolution, and potential habitability,” said Benz.
The upshot is that although we have plenty of ideas as to what form Proxima b will take, red dwarfs are the most common type of star in our galaxy. And if they have a preference for forming small, rocky worlds of a similar mass as Earth, statistically-speaking, there should be millions of “Earth 2.0″s out there in our galaxy with just the right quantities of water.
But do any of these worlds host life? For now, we can only speculate.
Researchers know little about the distant, icy planet Uranus compared to other planets in the solar system. Only one spacecraft has flown by it, Voyager 2 in 1986, and scientists have pieced together the rest of their observations through views from Earth-based and orbiting telescopes. The planet has rings — narrower and much darker in color than most of Saturn’s, with uneven widths and strange, sharp edges — and is tilted dramatically on its side, giving rise to decades-long seasons and extreme weather patterns.
Uranus has a crowded consortium of at least 27 moons named for literary figures, some orbiting in tight, unstable-looking formations. And now, new analysis of data from the Voyager 2 flyby suggests that two more tiny moons lurk even closer to the planet than those already known. [Photos of Uranus: A Strange, Tilted Planet]
Robert Chancia, a graduate student at University of Idaho, Moscow, investigated the patterns created when Voyager 2 beamed radio waves through the planet’s rings toward Earth. Based on how much light makes it through the rings, researchers can discern how much ring material there is at a particular spot, Chancia told Space.com.
And he found something unexpected around two thin inner rings, called alpha and beta: “At the edges of the rings … it’s almost like the amount of stuff is going up and down in a periodic fashion that looks kind of like a wave, with crests and troughs,” Chancia said. “It seems consistent with something disturbing the rings there,” he added.
The waves’ composition seem to reflect the rippling wake of a passing moon, Chancia said. Plugging the data into a model used to discover one of Saturn’s moons, the group found that the waves could be caused by small moonlets orbiting just outside each of the rings.
Although the moons would have moved on from their exact positions 30 years ago, the waves reveal their approximate masses and radial locations, which likely still apply today, Chancia said. To try and verify the new moons’ existence, Chancia combined Voyager 2 images of the planet in which the moons should have been visible. While other known moons were highlighted using this method, the potential new moonlets did not materialize.
“Based on the amplitude of this wave pattern and that distance from the ring … and our attempts to find the moon in images, it basically points toward if they exist, they’re pretty tiny,” Chancia said. That means the moons are likely smaller than 3 miles (5 kilometers) in radius, which would make them smaller and closer in than any of Uranus’ known moons. “The most likely scenario is that it’s a small object that’s right at the level of the noise in the images
Understanding Uranus’ rings, and the moons interacting with them, can help reveal more about the planet’s gravity and interior structure. Eight of Uranus’ nine main rings are very thin, less than 10 km (6 miles) thick, Chancia said. Researchers aren’t sure how the rings stay narrow over time when the particle collisions should cause them to spread out, or how long they’ve existed around the planet, but the actions of “shepherd moons” orbiting along with the rings may be keeping some of them in line. The moons Cordelia and Ophelia appear to keep Uranus’ outermost, widest ring relatively confined between around 20 and 100 km (12 and 62 miles) in width, for instance, and a similar setup may corral one of Saturn’s rings.
“Finding a small moon like this that could be helping to keep the alpha and beta rings confined and shed some light on that story could help — or just confuse things more,” Chancia said.
Mark Showalter, a researcher at SETI Institute in California, told New Scientist that the moons’ presence is “certainly a very plausible possibility.” Chancia said that Showalter and others can investigate data about Uranus from the Hubble Space Telescope to try to scope out traces of the two new moons. A lot of what scientists know about Uranus came from similar telescope observations, and this data offers the best opportunity to verify the moons’ existence, Chancia said — at least until some future mission approaches the ice giant once again.
The new work has been accepted to The Astronomical Journal, and is available online at the preprint site arXiv.
Humanity should be wary of seeking out contact with alien civilizations, Stephen Hawking has warned once again.
In 2010, the famed astrophysicist said that intelligent aliens may be rapacious marauders, roaming the cosmos in search of resources to plunder and planets to conquer and colonize. He reiterates that basic concern in “Stephen Hawking’s Favorite Places,” a new documentary streaming now on the CuriosityStream video service.
“One day, we might receive a signal from a planet like this,” Hawking says in the documentary, referring to a potentially habitable alien world known as Gliese 832c. “But we should be wary of answering back. Meeting an advanced civilization could be like Native Americans encountering Columbus. That didn’t turn out so well.”
For what it’s worth, some other astronomers believe Hawking’s caution is unwarranted. Any alien civilization advanced enough to come to Earth would surely already know of humans’ existence via the radio and TV signals that humanity has been sending out into space since 1900 or so, this line of thinking goes.
The alien musings are just a small part of “Stephen Hawking’s Favorite Places.” The 26-minute documentary shows the scientist zooming through the cosmos on a souped-up CGI spaceship called the “S.S. Hawking,” making five separate stops.
Hawking observes the Big Bang that created the universe, visits the monster black hole at the center of the Milky Way, journeys to Gliese 832c and tours Saturn in Earth’s own solar system. Then, he makes a final stop in Santa Barbara, California, which Hawking calls “my home away from home.”
“In 1974, Caltech [the California Institute of Technology] offered me a job in California,” the Englishman Hawking says in the documentary. “I jumped at the opportunity. In the sun with my young family, it was a world away from the gray skies of Cambridge, [England]. I’ve traveled the globe, but I’ve never found anywhere quite like this.”
You can watch a preview of “Stephen Hawking’s Favorite Places,” and learn how to subscribe to CuriosityStream, at the video service’s website: www.curiositystream.com.
The two objects straddle the dividing line between gas giants and odd “failed stars” known as brown dwarfs in terms of mass, researchers said. The newfound bodies are also similar to each other in size and age.
“They’re probably brother and sister,” Daniella Gagliuffi told Space.com. Gagliuffi, a graduate student at the University of California, San Diego, found the objects amid a cloud of stars about 65 light-years from Earth.
“It’s a little incestuous,” said Gagliuffi, who presented her research at the American Astronomical Society’s summer meeting in San Diego in June.
The pair lie within a dense cluster of stars that would normally be expected to strip objects away from one another. However, observations suggest that the two objects are so close that interactions with other stars would instead push them closer together, Gagliuffi said.
Planets or failed stars?
Galaxies are filled with stars, but they also include faint drifting objects with characteristics that make their status debatable. Such objects can be classified either as planets or as failed stars, given a blurry dividing line between the two.
That’s the case for the two objects Gagliuffi identified in a search for failed stars known as brown dwarfs. Gagliuffi sought brown dwarfs that could help her probe the lower boundary of what makes a star.
Unlike stars, brown dwarfs fail to fuse “normal” hydrogen in their interior. But these odd objects are apparently capable of fusing deuterium,
The newfound pair weigh in at roughly 15 and 14 times the mass of Jupiter. But the error bars associated with those estimates are wide enough that they may actually be in the planetary range.
“Their mass is straddling the deuterium-burning limit,” Gagliuffi said.
So, the twins could be a pair of planets dancing around a central point of mass (in which case they would be the history-making exoplanet binary), but they could also be a pair of brown dwarfs, or a brown dwarf hosting a massive gas giant planet.
To complicate the matter, both brown dwarfs and young gas giants produce light so weak that it is difficult to study their composition or differentiate them from one another.
And massive young planets produce heat from within, slowly cooling over their lifetimes. Gagliuffi’s studies show the pair are between 200 million and 300 million years old — young enough to confuse the issue.
Pairs of brown dwarfs are abundant throughout the Milky Way galaxy, but young binaries are not so common, Gagliuffi said. If the siblings turn out to be failed stars, they could provide intriguing insights into their family’s formation history.
Binary worlds also are thought to be rare. Our solar system is considered by some to host one pair of planets. The dwarf planet Pluto and its largest moon Charon orbit a point of mass outside the boundaries of each, making Pluto-Charon a binary system. No other binary planets are known outside of the sun’s orbit.
The newfound twin worlds drift through what Gagliuffi calls “a whole zoo of different stars,” only about 926 million miles (1.49 trillion kilometers) apart. While that sounds like an enormous distance — it is 10 times the distance between the Earth and the sun, after all— it’s actually extremely close for worlds from two different systems. She and her colleagues think it’s unlikely that the pair are just drifting close to one another by chance.
Given that they’re so close, it’s extremely likely that they’re bound,” Gagliuffi said.
It’s possible that the pair is connected to a third, more distant star that they orbit together. No such star has been identified, but many binary systems are actually triples, and Gagliuffi will look for a parent star as she continues this work.
Of course, the pair may also be drifting alone without adult supervision.
Is anyone else out there? Humans have asked this question ever since we could look up at the stars, but hundreds of thousands of years later, we still don’t have a satisfactory answer. Logic would seem to dictate that there’s other intelligent life out there, and yet it also suggests that if there is, it may have found us by now. While we may not have an answer for another few decades — if ever — we are slowly but surely getting closer.
A panel called “First Contact: Looking for Life in the Universe” at “Star Trek”: Mission New York Sept. 4 gave the audience a look at the current state of humanity’s search for extraterrestrial intelligence (SETI). The “Star Trek” mythos came up surprisingly few times for a panel calling itself a “Trek Talk,” but the subject matter was still appropriate, given the abundance of alien life on “Star Trek,” both familiar and bizarre. Dan Werthimer, the SETI chief scientist at the University of California, Berkeley, and Bobak Ferdowski from the NASA Jet Propulsion Laboratory oversaw the discussion, which covered the basics of astrobiology.
The two panelists spent a lot of time discussing the potential of finding life on Europa, an icy moon of Jupiter. Scientists have theorized that Europa has a liquid ocean buried beneath 30 miles of surface ice, and liquid water is potentially one of the most conducive environments for life to evolve, the panelists said. [13 Ways to Hunt for Intelligent Alien Life]
If we were to find life on Europa, Ferdowski and Werthimer explained, it would most likely be primitive. Humans may appear to be the dominant species on Earth, after all, but our overall biomass is pretty small when compared to wildly successful organisms such as bacteria, or even insects.
“Europa [may be] completely covered in water,” Werthimer explained. “That’s great for primitive life, but if you want technology, you’ve got to have some land surfaces as well.” Organisms on Earth, he said, have evolved to fill even the most extreme niches, “but it won’t necessarily evolve into something more complex than single-celled life … What are the pressures that make you want to go from ‘I can feed’ to standing and talking
In fact, the relative likelihood of finding primitive versus sapient life was one of the recurring themes of the talk. Werthimer believes that humanity may confirm the existence of primitive extraterrestrial life within the next 20 to 30 years, especially if scientists can get missions to Europa, but technological life is harder to pinpoint, as we don’t know how often it occurs.
Another potentially limiting factor is that intelligent life does not necessarily equate to technological life. Ferdowski and Werthimer pointed out that intelligent life (with varying degrees of what scientists would call “intelligence”) has evolved many times on Earth. Humans are the most obvious example, but dolphins, octopi and crows are all fairly clever creatures, to say nothing of the other great apes, which share a lineage with humans.
Even if there’s another technological civilization somewhere nearby, scientists are not exactly sure how to contact them. Radio signals seem like a safe bet; indeed, nearby stars have already seen “The Simpsons” and “I Love Lucy” from Earth’s TV broadcasts. On the other hand, while radio signals travel at the speed of light, that won’t do much good for an exoplanet that could be tens of thousands of light-years away.
On the flip side, given how fast life can (theoretically) arise and evolve on a planet, other civilizations could be millions or even billions of years ahead of Earth. We would have no idea how to monitor their communications, and they might not even be interested in ours.
Ferdowski and Werthimer contrasted the Drake Equation, which suggests that sapient life in the universe should be at least somewhat common, and the Fermi Paradox, which questions why alien life is not observable if the universe teems with it. One potential answer to the Fermi Paradox includes an alien version of the “Star Trek” Prime Directive, which prohibits interference with less advanced cultures. Another suggests that not all technological civilizations are necessarily driven by exploration, and may have directed their efforts inward to cultural matters instead.
Assuming that scientists can find life, however, there is (at least) one very important question to answer: Does it resemble humanity on a genetic level?
“Did it have a different biogenesis?” Ferdowski asked. “If it’s exactly the same as us, that probably doesn’t mean there were two independent origins of life.” In other words, if scientists find alien life that follows the basic biological dogma, such as translating DNA to RNA to proteins, it’s very likely that all life in the solar system originated from a common precursor
This theory, known as panspermia, suggests that extraordinarily simple, hardy life (or proto-life) could travel between planets aboard asteroids or other interplanetary debris. While this is harder to do once you get outside of a given solar system, it’s entirely possible that life on Earth and, say, Europa could have originated from the same predecessor, the researchers said.
While Ferdowski and Werthimer did not come to any hard conclusions as to whether or not humanity can expect to find life, they did say that the question has far-reaching consequences, regardless of the outcome.
“It’s a profound question either way,” Werthimer said. “If we find the universe is teeming with life, we can learn a lot. If we find out that we are alone, that somehow life is incredibly rare out of the trillion planets, that’s very profound also.
“If we find out we’re alone,” he added, “that means we’d better take incredibly good care of the precious life here on Earth.”
The sites of meteorite impacts on Mars are often considered to be good places to look for life. After all, it’s most likely that if any trace of life (past or present) ever took hold on the Red Planet, it would most likely be preserved under the bedrock of Mars’ harsh surface. Should there be a recent impact, could we search the debris to seek-out this recently excavated pristine rock for life?
Alas, in new research, this kind of impact crater search could be a fool’s errand; the energy of the impact likely sterilized any material we’d consider organic and related to life.
Researchers from Imperial College London carried out simulations of meteorite impacts in the lab to see how organic compounds fared when exposed to the kinds of impact pressures they could experience on Mars.
What they found wasn’t very promising if we hope to find evidence of life inside impact craters. For example, organic compounds associated with basic microbial and algal life (known as long chain hydrocarbon-dominated matter) were destroyed by the pressure of impact. On the other hand, other organic compounds associated with plant life (known as aromatic hydrocarbons) were chemically altered, but, according to a press release, “remained relatively resistant to impact pressures.”
Meteorites often contain organic chemicals not related to life that are resistant to the pressures of massive impacts.
So far, there has been little evidence of organics found that would suggest any kind of life has ever existed on Mars, but this new research provides an insight to what could be a previously overlooked complication in that search for life.
“We’ve literally only scratched the surface of Mars in our search for life, but so far the results have been inconclusive,” said Mark Sephton of Imperial College London. “Rocks excavated through meteorite impacts provide scientists with another unique opportunity to explore for signs of life, without having to resort to complicated drilling missions. Our study is showing us is that we may need to be nuanced in our approach to the rocks we choose to analyse.”
Rather than relying on computer simulations of meteorite impacts, the researchers used a piston cylindrical device to recreate the pressures and temperatures associated with a range of impact energies on various materials. They will continue to carry out these lab tests to see what energies give hypothetical Mars life the best chance of leaving their biological signature and which will pulverize their biology into oblivion.
“The study is helping us to see that when organic matter is observed on Mars, no matter where, it must be considered whether the sample could have been affected by the pressures associated with blast impacts,” added Wren Montgomery, also from Imperial. “We still need to do more work to understand what factors may play an important role in protecting organic compounds from these blast impacts. However, we think some of the factors may include the depths at which the rock records are buried and the angles at which meteorites hit the Martian surface.”
As we plan further exploration of the Martian surface, the more we can learn about where potential signs of Mars life could be hiding the better as, for now, we can’t assume that every crater will be a Mars biology goldmine.
Could there be a way to find bacterial structures on another planet? And if so, how important might these bacteria be in making a planet life-friendly? These are some of the questions that could be answered through studies on stromatolites, which are mounds of calcium-carbonate rock that are built up through lime-secreting cyanobacteria (bacteria that use photosynthesis for energy).
The research into the life-giving potential of these “living fossils” is based on small microbes in Australia, but the results could help us identify fossil evidence of life on other planets, in particular Mars, said Erica Suosaari, a science fellow for Bush Heritage Australia, a non-profit conservation and land management organization. Suosaari is based at Hamelin Station Reserve, Western Australia, a 500,000-acre property that borders one of the world’s most diverse and abundant examples of marine stromatolites, the Hamelin Pool Marine Nature Reserve.
“Looking for evidence of life in the rocks is like finding a needle in the haystack,” wrote Suosaari in an e-mail. “If stromatolites have definitive bio-signatures — such as self organized morphologies that are indicative of life processes — then it may be possible to look for that ‘signature’ in rocks on the surface of other planets and significantly reduce the size of that haystack
A paper based on Suosaari’s research at Hamelin Pool entitled “New multi-scale perspectives on the stromatolites of Shark Bay, Western Australia,” was published in the journal Scientific Reports earlier this year.
Funding for the collaborative research was provided by a consortium of oil companies (Chevron, Shell, Repsol and BP) who are interested in modern microbial carbonate environments to develop models for subsurface reservoirs and source rocks. Additional support for genomics analyses was provided by the Exobiology and Evolutionary Biology element of the NASA Astrobiology Program.
Learning more about ancient structures
On Earth, microbial communities responsible for creating stromatolites were essential in making the planet life-friendly. These stromatolite-forming cyanobacteria were the first living organisms to generate energy from the Sun using photosynthesis while creating oxygen as a byproduct. Over billions of years, cyanobacteria have changed Earth’s atmosphere from 1 percent oxygen to more than 20 percent oxygen, a composition that has allowed complex life evolve.
Suosaari’s research zeroes in on the stromatolites of Hamelin Pool, the most abundant and diverse modern assemblage of these microbial structures, which dominate nearly the entire 135 km of the coastline. Previous research into stromatolites identified them by the types of microbial mats colonizing the surface of the structure, a direct response of where the stromatolite resides in the tidal zone. Each lamination recorded in the stromatolite is thereby a record of a former surface mat. Her team instead classified stromatolites by their shape, revealing that certain shapes prefer to cluster in certain areas of the pool. Their investigation also showed that modern stromatolites have more in common with ancient stromatolites than previously thought.
“Modern marine stromatolites are often regarded as poor analogs of ancient stromatolites as a result of their grainy internal textures, which contrast with the fine grained nature of most ancient stromatolites,” Suosaari said.
By contrast, her team found out that in Hamelin Pool, the microbial communities commonly produce a fine-grained limestone known as micrite (microcrystalline calcite) creating stromatolite structures that are similar to the ancient stromatolites seen in the fossil record.
Furthermore, the stromatolite types in Hamelin Pool are dominated by a coccoid cyanobacterium that traces its lineage back 2 billion years to an ancient form of this cyanobacteria, called Eoentophysalis. This provides yet another similarity back to ancient times, Suosaari said. This means that standing along the shorelines of Hamelin Pool and gazing out onto the stromatolites, we are essentially looking through a window to early Earth at microbes of the same ancient lineage, pumping out oxygen and continuing to undertake processes that have been happening for billenia. There is not another place on the planet where this can be observed at such a scale.
The stromatolites studied were in a small region of Australia, but Suosaari said that as a whole, similar microbial communities could potentially be exported to other places — such as Mars — to make other locations in the Solar System more life-friendly to humans.
Suosaari said she thought of stromatolites when reading about SpaceX founder Elon Musk’s plans to bring life to the planet Mars. She suggested that because these stromatolite-building microbial communities produce oxygen, they could potentially make the Red Planet more life-friendly.
“Obviously with Elon Musk’s plans, we don’t have billions of years to shape the atmosphere if he is planning to move life there in the coming years, and Mars has less than 1 percent of the atmosphere of Earth,” she acknowledged. “But I begin to think about photosynthesizing microbial mats and how they have prevailed for billions of years; it’s a kind of resilience and longevity that our species hasn’t yet achieved. Perhaps we should look to these microbial communities to generate oxygen on the Red Planet at a small scale.”
The space agency announced Friday that plans are moving ahead for the robotic rover to launch in the summer of 2020 and land on Mars in February 2021.
The new rover also is designed to test the planet for usable resources, such as oxygen, that will be needed for future missions to Mars that will include humans.
The Mars Curiosity rover, which has been working on the Red Planet since August 2012, has been searching for evidence that the planet could have ever sustained life – even in microbial form.
The new rover will take the next step, looking for evidence of life.
“The Mars 2020 rover is the first step in a potential multi-mission campaign to return carefully selected and sealed samples of Martian rocks and soil to Earth,” said Geoffrey Yoder, acting associate administrator of NASA’s Science Mission Directorate, in a statement. “This mission marks a significant milestone in NASA’s Journey to Mars – to determine whether life has ever existed on Mars, and to advance our goal of sending humans to the Red Planet.”
The new vehicle, unofficially dubbed the Mars 2020 rover, is expected to explore a region of the planet where NASA scientists expect that the ancient environment had been favorable to support microbial life.
The rover will drill into rocks, collect samples and ready them for a return trip to Earth as part of a future Mars mission.
In an attempt to save money on the project, NASA plans to base the rover’s design on that of its predecessor, Curiosity.
Scientists want to study the samples for evidence of past life but also for materials that could pose a threat to humans on a future Mars mission.
NASA is expected to send astronauts to Mars in the 2030s.
As NASA’s New Horizons probe speeds toward a possible encounter with an object beyond the orbit of Pluto, the spacecraft has made observations of another icy object located in the same outer region of the solar system.
New Horizons finished its close encounter with Pluto last July and since then has completed two sets of observations on an object in the Kuiper Belt, the band of objects beyond the orbit of Neptune. The icy body is known as 1994 JR1 and orbits about 32 astronomical units away from the sun (an astronomical unit is the distance from the Earth to the sun). New Horizons’ view of the faint, icy body can be seen in this video from Space.com.
The observations put a stop to the hypothesis that JR1 may be a satellite of Pluto, New Horizons science team member Simon Porter said in a statement from NASA.
“Combining the November 2015 and April 2016 observations allows us to pinpoint the location of JR1 to within 1,000 kilometers (about 600 miles), far better than any small [Kuiper Belt object],” said Porter, a postdoctoral planetary scientist at the Southwest Research Institute in Colorado.
The team also figured out how fast the 90-mile-wide (150 km) object is rotating, using observations taken in April. Changes in light reflected off of JR1’s surface showed that the object rotates once every 5.4 hours, which is considered relatively quick for a KBO.
These observations will serve as practice for the possible 20 other objects New Horizons can see in the Kuiper Belt through its extended mission. If the New Horizons extended mission receives approval from NASA, the probe will do close-up observations of 2014 MU69 on Jan. 1, 2019.
New atmospheric insights
Meanwhile, researchers continue to analyze data from last year’s Pluto encounter. Team members now have new insights into the dwarf planet’s tenuous atmosphere after looking at starlight passing through the wispy gas, according to the NASA statement.
Roughly four hours after New Horizons made its closest approach to Pluto, on July 14, the spacecraft’s ultraviolet spectrometer instrument looked at two stars moving behind Pluto and its atmosphere (astronomers call this a stellar occultation).
“The light from each star dimmed as it moved through deeper layers of Pluto’s atmosphere, absorbed by various gases and hazes,” NASA wrote in a second press release.
The spectrometer confirmed previous measurements from New Horizons showing that Pluto’s upper atmosphere is up to 25 percent colder (and thus more compact) than what scientists expected before New Horizons flew by. The instrument also confirmed a calculation that nitrogen molecules escape the dwarf planet’s atmosphere at a rate of about 1,000 times lower than expected.
Stellar occultations of 1994 JR1 were also performed using light from the sun. This allowed New Horizons to confirm the atmospheric temperature and structure, measure the escape rate of nitrogen molecules from the atmosphere, and detect the presence of various gases (including nitrogen, methane and acetylene).
Some of Saturn’s icy moons may have been formed after many dinosaurs roamed the Earth. New computer modeling of the Saturnian system suggests the rings and moons may be no more than 100 million years old.
Saturn hosts 62 known moons. All of them are influenced not only by the gravity of the planet, but also by each other’s gravities. A new computer model suggests that the Saturnian moons Tethys, Dione and Rhea haven’t seen the kinds of changes in their orbital tilts that are typical for moons that have lived in the system and interacted with other moons over long periods of time. In other words, these appear to be very young moons.
“Moons are always changing their orbits. That’s inevitable,” Matija Cuk, principal investigator at the SETI Institute and one of the authors of the new research, said in a statement. “But that fact allows us to use computer simulations to tease out the history of Saturn’s inner moons. Doing so, we find that they were most likely born during the most recent 2 percent of the planet’s history.
The age of Saturn’s rings has come under considerable debate since their discovery in the 1600s. In 2012, however, French astronomers suggested that some of the inner moons and the planet’s well-known rings may have recent origins. The researchers showed that tidal effects — which refer to “the gravitational interaction of the inner moons with fluids deep in Saturn’s interior,” according to the statement — should cause the moons to move to larger orbits in a very short time.
“Saturn has dozens of moons that are slowly increasing their orbital size due to tidal effects. In addition, pairs of moons may occasionally move into orbital resonances. This occurs when one moon’s orbital period becomes a simple fraction of another. For example, one moon could orbit twice as fast as another moon, or three times as fast.
Once an orbital resonance takes place, the moons can affect each other’s gravity, even if they are very small. This will eventually elongate their orbits and tilt them from their original orbital plane.
By looking at computer models that predict how extended a moon’s orbit should become over time, and comparing that with the actual position of the moon today, the researchers found that the orbits of Tethys, Dione and Rhea are “less dramatically altered than previously thought,” the statement said. The moons don’t appear to have moved very far from where they were born.
To get a more specific value for the ages of these moons, Cuk used ice geysers on Saturn’s moon Enceladus. The researchers assumed that the energy powering those geysers comes from tidal interactions with Saturn and that the level of geothermal activity on Enceladus has been constant, and from there, inferred the strength of the tidal forces from Saturn.
Using the computer simulations, the researchers concluded that Enceladus would have moved from its original orbital position to its current one in just 100 million years — meaning it likely formed during the Cretaceous period. The larger implication is that the inner moons of Saturn and its gorgeous rings are all relatively young. (The more distant moons Titan and Iapetus would not have been formed at the same time.)
“So the question arises — what caused the recent birth of the inner moons?” Cuk said in the statement. “Our best guess is that Saturn had a similar collection of moons before, but their orbits were disturbed by a special kind of orbital resonance involving Saturn’s motion around the sun. Eventually, the orbits of neighboring moons crossed, and these objects collided. From this rubble, the present set of moons and rings formed.”
The research is being published in the Astrophysical Journal