Scientists have found a strange structure resembling a microbial cell inside a Martian meteorite, but they’re not claiming that it’s evidence of Red Planet life.
The researchers discovered the microscopic oval object within the Nakhla Mars meteorite, which fell to Earth in Egypt in 1911. While the structure’s appearance is intriguing, it most likely formed as a result of geological rather than biological processes, team members said.
“The consideration of possible biotic scenarios for the origin of the ovoid structure in Nakhla currently lacks any sort of compelling evidence,” the scientists write in a new study published this month in the journal Astrobiology. “Therefore, based on the available data that we have obtained on the nature of this conspicuous ovoid structure in Nakhla, we conclude that the most reasonable explanation for its origin is that it formed through abiotic processes.” [The Search for Life on Mars (A Photo Timeline)]
A cell-like structure
The hollow ovoid is about 80 microns long by 60 microns wide, researchers said — far larger than most terrestrial bacteria but in the normal size range for eukaryotic Earth microbes (single-celled organisms that possess nuclei and other membrane-bound interior “organelles”). The study team is confident that the object is native to the sample and not the result of terrestrial contamination.
The scientists studied the structure using a number of different techniques, including electron microscopy, X-ray analysis and mass spectrometry. This work revealed that the ovoid is composed of iron-rich clay and contains a number of other minerals.
The researchers run through a number of possible formation scenarios in the new study, eventually concluding that the ovoid most likely formed when materials partially filled in a pre-existing vesicle — a vapor bubble, for example — in the rock.
But this supposition doesn’t rule out the possibility that Martian lifeforms had something to do with the structure, team members said.
“Despite the extremely biomorphic overall shape of the ovoid, it is highly unlikely that it itself was an organism,” said lead author Elias Chatzitheodoridis, of the National Technical University of Athens in Greece.
“However, it could have been formed directly by micro-organisms, or it could trap organic material that came from elsewhere,” Chatzitheodoridis told Space.com via email. “That the ovoid is hollow means that there is enough space to accommodate colonies of microorganisms.”
Making a firm link to Mars life would require further study and further discoveries, he added.
“We would be happy if we could have found more than one ovoid, with exactly the same texture both in the micro and the nanoscale,” Chatzitheodoridis said. “However, we require to open up enough sample in a very careful way. Compelling evidence, though, would be if we could really find many of the same, clearly in a form of a colony, together with chemical and mineralogical biosignatures that are common for terrestrial microbes.”
Habitable Martian environments?
Nakhla is a well-studied meteorite — scientists have spotted possible signs of Mars life within it before —and previous research has mapped out its history in some detail. Nakhla’s parent rock apparently crystallized about 1.3 billion years ago, Chatzitheodoridis and his colleagues write in the new study, then experienced two shock events that heated it up considerably.
The first of these shocks likely occurred around 910 million years ago and the second 620 million years ago. This latter event, which was triggered by a nearby meteorite strike on Mars, apparently included the flow of hot water through Nakhla’s parent outcrop, the authors write. Finally, about 10 million years ago, another impact blasted Nakhla free of Mars, sending it on a looping trip through space that ended with its arrival at Earth in 1911.
Whether or not the Nakhla ovoid has some connection to Martian life, study of the meteorite can help researchers better understand the Red Planet’s past (and, perhaps, present) potential to support life, Chatzitheodoridis said.
Martian meteorites contain “important information, and latest work has shown that now one has to look more carefully at them and in finer detail,” he told Space.com.
“In our case, it is such work that allowed us to see from a small volume of sample a big story, i.e., that hydrothermal waters have actually acted also in the latest periods of Martian history, even if they were caused by a bolide impact, and that they were capable of initiating a number of complicated processes that resulted in the formation of niche environments which can sustain life, if life [ever] emerged on the planet,” Chatzitheodoridis added.
Such exoplanets could potentially be the longest-lived life-friendly areas in the universe, enduring for up to 10 trillion years, scientists added.
As planets age, they cool, with their hot molten cores solidifying over time. This probably makes them geologically active and therefore less habitable for life as we know it, scientists say. On Earth, life depends on the geological activity of plate tectonics to circulate rocks that can absorb or release carbon dioxide, a greenhouse gas that absorbs heat. Without plate tectonics, the planet might experience runaway heating or cooling, and thus potentially become uninhabitable.
In a new study, scientists have found that if a world has a companion planet that gravitationally tugs on it, this could prevent that world from cooling, and thus extend its chances of hosting life.
Strange twin worlds
The researchers analyzed red dwarfs stars, also known as M dwarf stars. These stars are up to 50 times dimmer than the sun and up to less than 10 percent as massive. Red dwarfs are the most common kind of star, making up to 70 percent of the stars in the universe, and this fact has made scientists wonder if these red dwarfs might be the best places to look for alien life.
Because there is life nearly wherever there is water on Earth, scientists typically define planets as potentially habitable if their surfaces are warm enough to sustain water on their surfaces. Red dwarfs are cold stars, which means their habitable zones are closer than Mercury is to the sun — sometimes less than 0.1 astronomical units (AU), or one-tenth the average distance from Earth to the sun. The average distance between Earth and the sun is about 93 million miles (150 million kilometers).
Red dwarfs are colder than the sun, which means they burn fuel more slowly and live far longer. Prior research has suggested that the most readily discoverable Earth-size habitable-zone planets are likely to be about 10 billion years old — more than twice the age of 4.6-billion-year-old Earth.
Ordinarily, plate tectonics ends due to cooling long before a planet reaches 10 billion years in age. However, the researchers found that if this old world has a companion planet orbiting a bit farther away from the star, this outer planet can pull the old world into an orbit that will keep it warm enough for plate tectonics.
Rocky companion planet pals
The scientists modeled a rocky planet with the same mass and diameter as Earth’s in the habitable zone of a red dwarf just 10 percent of the sun’s mass. This red dwarf is about 1,000 times less luminous than the sun, meaning its habitable zone is only about 3 percent of an AU.
The researchers modeled outer planets with masses equal to those of Earth, Neptune, Saturn, Jupiter and larger. They found that the gravitational pulls of outer planets with a variety of masses and orbits can drag an inner rocky planet into an eccentric oval-shaped orbit. This means that the distance of the inner planet from its star changes over time.
“When the planet is closer to the star, the gravitational field is stronger, and the planet is deformed into an American football shape,” study co-author Rory Barnes, an astrobiologist and planetary scientist at the University of Washington in Seattle,said in a statement. “When farther from the star, the field is weaker, and the planet relaxes into a more spherical shape.”
This constant tidal flexing causes layers inside the planet to rub against each other, producing warmth. This effect, known as tidal heating, is what drives volcanism on Jupiter’s moon Io.
“For planets in the habitable zone around low-mass stars, tides raised on the planet by the star can be very important,” lead study author Christa Van Laerhoven, a planetary scientist who will soon be a postdoctoral researcher at the Canadian Institute for Theoretical Astrophysics in Toronto, told Space.com. “Tides raised on the habitable zone planet by its star can provide a long-term internal heat source if there is another well-placed planet in the system.”
Tidal heating could help keep a rocky planet internally warm and tectonically active in the habitable zone of a red dwarf for the star’s lifetime of up to 10 trillion years, or more than 700 times the 13.7-billion-year history of the universe, Barnes said.
“Perhaps in the distant future, after our sun has died out, our descendants will live on worlds like these,”Barnes said in a statement.
The researchers suggested that if astronomers were to find any Earth-size planetsin the habitable zones of red dwarfs, they should follow up with searchers for outer companion planets that might improve the inner world’s chance at hosting life. In the future, they also hope to model systems with three or more planets.
Van Laerhoven, Barnes and their colleague Richard Greenberg detailed their findings in the July issue of the journal Monthly Notices of the Royal Astronomical Society.
The solar system coalesced from a huge cloud of dust and gas that was isolated from the rest of the Milky Way galaxy for up to 30 million years before the sun’s birth nearly 4.6 billion years ago, a new study published online today (Aug. 7) in the journal Science suggests. This cloud spawned perhaps tens of thousands of other stars as well, researchers said.
If further work confirms these findings, “we will have the proof that planetary systems can survive very well early interactions with many stellar siblings,” said lead author Maria Lugaro, of Monash University in Australia.
“In general, becoming more intimate with the stellar nursery where the sun was born can help us [set] the sun within the context of the other billions of stars that are born in our galaxy, and the solar system within the context of the large family of extrasolar planetary systems that are currently being discovered,” Lugaro told Space.com via email.
A star is born
Radiometric dating of meteorites has given scientists a precise age for the solar system — 4.57 billion years, give or take a few hundred thousand years. (The sun formed first, and the planets then coalesced from the disk of leftover material orbiting our star.)
But Lugaro and her colleagues wanted to go back even further in time, to better understand how and when the solar system started taking shape.
This can be done by estimating the isotope abundances of certain radioactive elements known to be present throughout the Milky Way when the solar system was forming, and then comparing those abundances to the ones seen in ancient meteorites. (Isotopes are versions of an element that have different numbers of neutrons in their atomic nuclei.)
Because radioactive materials decay from one isotope to another at precise rates, this information allows researchers to determine when the cloud that formed the solar system segregated out from the greater galaxy — that is, when it ceased absorbing newly produced material from the interstellar medium.
Estimating radioisotope abudances throughout the Milky Way long ago is a tall order and involves complex computer modeling of how stars evolve, generate heavy elements in their interiors and eventually eject these materials into space, Lugaro said.
But she and her team made a key breakthrough, coming up with a better understanding of the nuclear structure of one radioisotope known as hafnium-181. This advance led the researchers to a much improved picture of how hafnium-182 — a different isotope whose abundances in the early solar system are well known — is created inside stars.
“I think our main advantage has been to be a team of experts in different fields: stellar astrophysics, nuclear physics, and meteoritic and planetary science so we have managed to exchange information effectively,” Lugaro said.
A long-lasting stellar nursery
The team’s calculations suggest that the solar system’s raw materials were isolated for a long time before the sun formed — perhaps as long as 30 million years.
“Considering that it took less than 100 million years for the terrestrial planets to form, this incubation time seems astonishingly long,” Martin Bizzarro, of the University of Copenhagen in Denmark, wrote in an accompanying “Perspectives” piece in the same issue of Science.
Bizzarro, like Lugaro, thinks the new results could have application far beyond our neck of the cosmic woods.
“With the anticipated discovery of Earthlike planets in habitable zones, the development of a unified model for the formation and evolution of our solar system is timely,” Bizarro wrote. “The study of Lugaro et al. nicely illustrates that the integration of astrophysics, astronomy and cosmochemistry is the quickest route toward this challenging goal.”
The researchers plan to investigate other heavy radioactive elements to confirm and refine their timing estimates, Lugaro said.
The abstract of the new study can be found here, while this link leads to the abstract of Bizzarro’s companion piece.
Only a handful of these rapid, millisecond-duration events, known as “fast radio bursts” (FRBs), had been detected previously, all of them by a single instrument — the Parkes Observatory in Australia. As a result, some astronomers have speculated that FRBs have local origins.
But the latest burst, which was observed on Nov. 2, 2012 by the Arecibo radio telescope in Puerto Rico, puts the lie to that notion, researchers said.
“Our result is important because it eliminates any doubt that these radio bursts are truly of cosmic origin,” study co-author Victoria Kaspi, of McGill University in Montreal, Canada, said in a statement. “The radio waves show every sign of having come from far outside our galaxy — a really exciting prospect.”
Kaspi is principal investigator of the Pulsar ALFA (PALFA) survey, a search for pulsars — fast-spinning, super-dense objects that emit beams of light (which appear to pulse at a regular interval, because they can be observed only when the pulsar is pointed at Earth). The research team, led by Laura Spitler of the Max Planck Institue in Germany, discovered the new FRB in the PALFA data.
The newly observed burst is the first of its kind discovered by a telescope other than Parkes, researchers said.
“The brightness and duration of this event, and the inferred rate at which these bursts occur, are all consistent with the properties of the bursts previously detected by the Parkes telescope in Australia,” said Spitler, who was completing her PhD at Cornell University when the research began.
The short lifetime of FRBs makes it tough to study them; only seven events, including the newest burst, have been recorded since their 2007 discovery. But the new study should help researchers get a better grip on FRBs.
Their presumed extragalactic origins mean that fast radio bursts could provide unprecedented opportunities to study the intergalactic medium — the dust and gas between galaxies — according to the research paper, which was published in the Astrophysical Journal.
By extrapolating how much of the sky was studied and for how long, scientists have calculated that FRBs probably occur roughly 10,000 times a day. Based on this occurrence rate, PALFA is expected to find two to three more FRBs in the coming years.
The source of fast radio bursts remains a mystery that astrophysicists are eager to solve. A number of exotic possibilities include evaporating primordial black holes, merging or collapsing neutron stars and superconducting cosmic strings. Flares from magnetically active neutron stars, known as magnetars, could also be responsible for the events, researchers said.
Extremely bright flashes from pulsars outside the galaxy are another possibility. The research team suggested that FRBs could be pulses that repeat over even longer timescales than anticipated. If this is the case, longer observation times would be required to spot them.
“We cannot be certain that the bursts are non-repeating,” the team wrote in the paper. “Detecting an astrophysical counterpart will be an important step in determining whether we expect repeated events.”
In our solar system, the orbits of most planets are nearly circular, orbiting the sun’s equator. However, many of the exoplanets astronomers have discovered in the past two decades or so have mysteriously skewed orbits. They may be eccentric — that is, oval-shaped. They could also be inclined — tilted at an angle from the equators of their stars.
One potential explanation for these skewed orbits might be the gravitational influence of a companion star near the host stars of those exoplanets. Although the sun is a solitary star, most stars form in binary pairs, with both stars orbiting each other. In fact, there are many three-star systems as well, and even some that harbor up to seven stars.
Now, astronomers have captured the clearest picture yet of planet-forming disks around binary stars. They found these disks may be wildly misaligned around their stars, hinting that exoplanets may often be found in eccentric or inclined orbits from the moment they are born.
The researchers made this discovery while surveying a series of binary stars using the Atacama Large Millimeter/submillimeter Array (ALMA) of radio telescopes in Chile. ALMA is the largest and most expensive ground-based astronomical project to date.
The scientists focused on the two stars in the young HK Tauri system, which is about 450 light-years from Earth in the constellation of Taurus. These stars are less than 5 million years old and are separated by about 36 billion miles (58 billion kilometers), or 13 times the distance of Neptune from the sun.
Stars and planets form out of vast clouds of dust and gas. As the material in these clouds contracts under gravity, it begins to rotate until most of the dust and gas falls into flattened disks swirling around stars. Eventually worlds are born from these protoplanetary disks.
The star in the pair that looks dimmer, HK Tauri B, appears that way because the protoplanetary disk around it blocks out much of its light. The disk itself, however, can be easily observed by the visible and near-infrared starlight it scatters.
The star that appears brighter, HK Tauri A, also has a protoplanetary disk, but it is tilted in a way that does not block out its star’s light. Therefore, the disk cannot be seen in visible light because its faint glow is swamped by the dazzling brightness of its star. This disk does shine brightly in millimeter-wavelength light, however, which ALMA can readily detect. [7 Ways to Discover Alien Planets]
Using ALMA’s unprecedented resolution and sensitivity, the researchers successfully measured the rotation of HK Tauri A’s disk. This revealed the two disks are tilted with each other by at least 60 degrees. This means that instead of being in the same plane as the orbits of the two stars, at least one of the disks must be significantly misaligned.
“What was surprising to me was how clearly the result — misalignment of the disks — popped out of the data when we were first looking at it,” said study author Eric Jensen, an astronomer at Swarthmore College in Pennsylvania. “That’s partly a testament to the high quality of the data from ALMA, but partly a result of just how misaligned the two disks are with each other.”
Since material that will eventually form planets is in skewed orbits around these stars, the worlds that emerge from these disks may also end up in eccentric or inclined orbits. “Binary star companions may influence the orbits of planets, possibly explaining some, though not all, of the weird orbits we see among extrasolar planets,” Jensen told Space.com.
However, most exoplanets with skewed orbits are not in known binary systems.
“There are almost certainly some of these systems that have low-mass binary companions that haven’t been discovered yet, but that won’t be the case for all systems,” Jensen said. “So while this binary-star-driven mechanism can explain some of the misaligned systems, it can’t explain everything. That’s an interesting puzzle that people are still working on.”
One probable mechanism for what causes exoplanets to have skewed orbits around solitary singleton stars is interactions among the planets in those systems.
“If you form a lot of planets around a given star, especially if their orbits are pretty closely packed together, you are going to have interactions between planets, which can change their orbits,” Jensen said. “In fact, even in our own solar system, people think that Uranus and Neptune have been pushed into wider orbits than those in which they originally formed, due to interactions with Jupiter and Saturn.”
In the future, the researchers want to look at more binary systems with protoplanetary disks to see how typical or atypical skewed disks are. Jensen and his colleague Rachel Akeson detailed their findings in the July 31 issue of the journal Nature.
In fact, clouds might help Earth-like planets remain hospitable to life even when orbiting a sun-like star as closely as the hellish Venus circles the sun in our solar system, the scientists added.
This finding suggests that many alien worlds previously thought to be too hot for life as we know it may actually be habitable, investigators said.
Astronomers have confirmed the existence of more than 1,700 worlds beyond the solar system in the past 20 years, and may soon prove the existence of thousands more such exoplanets. Of key interest are exoplanets in habitable, or Goldilocks, zones, the regions around stars just warm enough to possess liquid water on their surfaces, as there is life virtually wherever liquid water is found on Earth.
Habitable alien planets
The distance at which a planet orbits its star is one factor behind how much light from the star heats up that world’s surface. Another factor controlling how much energy a planet gets from its star are clouds in that world’s atmosphere, which can reflect light away from a world and cool it down — for instance, clouds account for most of the sunlight reflected away from Earth. [Habitable Zones for Alien Planets Explained (Infographic)]
Now scientists find that on planets that rotate much slower than Earth, clouds form that can help those worlds maintain Earth-like climates, even when they receive levels of light from their stars that would make Earth uninhabitable for life as we know it.
The amount of clouds a planet has and where these clouds are located on that world are primarily controlled by how its atmosphere circulates. This in turn is determined in part by how slowly that planet spins. For instance, the more slowly a planet rotates, the longer both its days and nights are — this increases the difference in temperature between the day and night sides, and to even out this imbalance, the atmosphere will circulate more.
In addition, when a planet spins, masses of air on its surface will rotate as well, a phenomenon known as the Coriolis effect that influences how powerfully major wind patterns such as hurricanes whirl. The faster a world spins, the stronger the Coriolis effect, and the more the atmosphere will separate into multiple bands running parallel to the equator in which the winds circulate in distinct patterns. The slower a planet whirls, the weaker the Coriolis effect, and the less divided the atmosphere will be into distinct regions.
Cloudy with a chance of life?
To investigate the effects of a planet’s rotation on its habitability, scientists investigated how three-dimensional models of atmospheric circulation behaved on computer-simulated planets with the same mass and diameter as the Earth. These virtual worlds had rotation speeds ranging from twice as fast as Earth’s to 365 times slower than Earth’s, and received from about 0.25 to 2.5 times as much light from their stars as Earth does.
On Earth, cloud formation begins when heat from the sun causes water to evaporate. As this invisible water vapor rises, it cools and condenses into clouds of visible water droplets or ice crystals.
The scientists found that on what they considered rapidly rotating planets — ones that rotated about as fast as Earth — the atmosphere broke up into distinct bands, and clouds behaved much like they do on Earth. The habitable zones of these rapidly rotating worlds matched previous calculations for planets in general.
However, slowly rotating planets — ones that spin 100 times slower than Earth or more — had significantly wider habitable zones. They could maintain Earth-like climates even when receiving nearly twice as much light as rapidly rotating planets.
The scientists explained that on slowly rotating planets, the area on the planet that faces its star — the “substellar point” — gets heated for a long time. This causes air to rise from the substellar point.
“Clouds tend to form where air rises because moist warm air is cooled, leading to condensation,” said study co-author Dorian Abbot, a geophysicist at the University of Chicago.
Without a strong Coriolis effect to break up atmospheric circulation into distinct bands, more clouds form. At the substellar point, the researchers found cloud cover would be present 90 percent or more of the time, reflecting a significant amount of light away from the planet, Abbot said.
Venus-like planets and life
Intriguingly, “the model finds a habitable climate for a planet with Earth’s atmosphere in Venus’ orbit with Venus’ rotation rate because of increased cloud cover,” Abbot told Space.com. In comparison, Venus rotates more than 240 times slower than Earth, and orbits the sun at a distance of less than three-quarters of an astronomical unit (AU), the average distance from Earth to the sun, where it receives nearly twice as much light from the sun as Earth.
However, Venus is a hellish planet that is definitely not habitable. Temperatures on Venus reach 870 degrees F (465 degrees C), more than hot enough to melt lead. This makes the surface of Venus extremely dry — there is no liquid water on its surface because the scorching heat would cause any to boil away. The researchers suggest that Venus once rotated more rapidly, at a rate only about 10 to 100 times slower than Earth’s, which helped make it uninhabitable.
The researchers suggest their findings should be checked with other climate models and with more sophisticated cloud models. They detailed their findings in the April 25 edition of the Astrophysical Journal Letters.
Using observations by NASA’s Kepler and Spitzer space telescopes, researchers determined that the exoplanet Kepler-93b is 1.48 times the size of Earth, confirming its status as a super-Earth — a world slightly larger than our own — and allowing scientists to conclude that the planet is very likely composed of iron and rock.
“With Kepler and Spitzer, we’ve captured the most precise measurement to date of an alien planet’s size, which is critical for understanding these far-off worlds,” lead author Sarah Ballard, of the University of Washington in Seattle, said in a statement. “The measurement is so precise that it’s literally like being able to measure the height of a six-foot-tall person to within three-quarters of an inch — if that person were standing on Jupiter.” [The Strangest Alien Planets]
Kepler-93b, which lies about 300 light-years away, orbits a star that’s about 90 percent as wide and massive as the sun. The rocky planet circles its host at only one-sixth the distance Mercury orbits the sun, resulting in a likely surface temperature of around 1,400 degrees Fahrenheit (760 degrees Celsius).
Ballard and her team used a new observing technique developed for Spitzer, combined with frequent observations from Kepler, to confirm that Kepler-93b is indeed a planet rather than a false positive.
The two telescopes noted how much the star dimmed as the planet crossed its face. In the visible-light wavelengths observed by Kepler and the infrared wavelengths captured by Spitzer, the signal remained the same.
In addition, Kepler studied the stellar dimming caused by seismic waves within the star, making it one of the lowest-mass targets of astroseismic study. These measurements allowed for a more precise computation of the star’s radius, which in turn led to a more refined solution for the planet’s width, researchers said.
The combined data reveal that Kepler-93b boasts a diameter of approximately 11,700 miles (18,800 kilometers), with an error of only about 150 miles (240 km) — the approximate distance from Washington, D.C., to Philadelphia.
Combined with Kepler-93b’s previously computed mass of approximately 3.8 times that of Earth, the refined radius allowed scientists to calcuate that the planet’s density is nearly twice that of Earth. This implies that iron and rock dominate the composition of Kepler-93b, researchers said.
The planet’s temperature and proximity to its star make it unlikely that Kepler-93b could hold on to gases at its surface. However, based on its physical measurements, Ballard and her team found a 3 percent chance that it could contain an extended atmosphere.
“Ballard and her team have made a major scientific advance while demonstrating the power of Spitzer’s new approach to exoplanet observations,” said Michael Werner, Spitzer’s project scientist.
Spitzer may not be able to keep making such measurements for much longer. In May, a NASA senior review panel recommended ending the mission, which launched in 2003, unless additional funding can be found.
The research was published in the Astrophysical Journal.
A new test could determine once and for all whether NASA’s Voyager 1 probe has indeed entered interstellar space, some researchers say.
While mission team members declared last year that Voyager 1 reached interstellar space in August 2012, not all scientists are sold. Two researchers working with Voyager 1 have drawn up a test to show whether the spacecraft is inside or outside of the heliosphere — the bubble of solar particles and magnetic fields that the sun puffs around itself.
The scientists who came up with the test predict that Voyager 1 will cross the current sheet — a huge surface within the heliosphere — at some point within the next one to two years. When that happens, Voyager team members should see a reversal in the magnetic field surrounding the probe, proving that it is still within the heliosphere. If this change doesn’t occur in the next two years or so, then Voyager is almost certainly already in interstellar space, researchers said.
“The proof is in the pudding,” George Gloeckler of the University of Michigan, lead author of the new study detailing the test, said in a statement. “This controversy will continue until it is resolved by measurements.”
Scientists have recently made measurements that seem to bolster the belief that Voyager is in interstellar space. Researchers measuring data from a solar eruption that shook the particles around Voyager 1 found that the density of the probe’s surroundings was much higher than earlier measurements, when it was thought to be inside the heliosphere.
Because of this difference, some team members have come to the conclusion that Voyager 1 is, in fact, outside of the heliosphere. (While particle densities are higher in the inner solar system than they are in interstellar space, this is not the case at the extreme outer reaches of the heliosphere, scientists said.)
Voyager 1 has measured cosmic rays and other signs indicating that it may have passed into interstellar space, it still hasn’t detected the predicted magnetic field change, Gloeckler pointed out. He expects that the polarity reversal may happen in 2015.
“If that happens, I think if anyone still believes Voyager 1 is in the interstellar medium, they will really have something to explain,” Gloeckler said in the statement. “It is a signature that can’t be missed.”
The developers of the new test think Voyager 1 is moving faster than the solar wind, meaning that it will cross over parts of the current sheet where the magnetic field reversal will happen. This data could prove that the probe is inside the heliosphere, according to a statement from the University of Michigan and the American Geophysical Union.
Other scientists working with Voyager also welcome the test.
“It is the nature of the scientific process that alternative theories are developed in order to account for new observations,” Ed Stone, NASA’s Voyager project scientist, said in a statement. “This paper differs from other models of the solar wind and the heliosphere and is among the new models that the Voyager team will be studying as more data are acquired by Voyager.”
Voyager 1 and its twin Voyager 2 launched to space in 1977 to study the planets of the solar system. Voyager 2 is still in communication with Earth and is expected to continue on, potentially entering into interstellar space a few years from now.
The new test, detailed in a study by Gloeckler and his co-author Len Fisk of the University of Michigan, has been accepted for publication in the journal Geophysical Research Letters.
The alien planet Kepler-421b — which crosses the face of, or transits, its host star from Earth’s perspective — takes 704 Earth days to complete one orbit, and thus has the longest year known for any transiting alien world, researchers said. (For comparison, Earth orbits the sun once every 365 days, and Mars completes a lap every 780 days.)
“Finding Kepler-421b was a stroke of luck,” study lead author David Kipping, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said in a statement. “The farther a planet is from its star, the less likely it is to transit the star from Earth’s point of view. It has to line up just right.” [10 Exoplanets That Could Host Alien Life]
To be clear, Kepler-421b does not have the longest year of any known alien planet. Many nontransiting worlds have much more far-flung orbits, including the gas giant GU Piscium b, which takes about 160,000 years to complete a lap around its host star.
Kepler-421b, which is about the size of Uranus, is located about 1,000 light-years from Earth, in the constellation Lyra. It was spotted by NASA’s Kepler space telescope, which launched in March 2009 to hunt for transiting exoplanets by noting the tiny brightness dips caused when they cross in front of their stars.
Kepler has found nearly 1,000 alien worlds to date and has flagged more than 3,000 other “candidates” that still need to be confirmed by follow-up observations or study. Mission team members expect that at least 90 percent of these candidates will eventually turn out to be bona fide planets.
The spacecraft suffered a glitch in May 2013 that ended its original mission, but NASA recently signed off on a new mission, called K2, that will keep Kepler hunting for exoplanets, in addition to other cosmic bodies and phenomena.
Most of Kepler’s finds thus far are worlds that orbit relatively close to their parent stars, since such planets transit relatively frequently. The instrument has generally required three transits to conclusively identify an exoplanet, but Kepler-421b was detected after it crossed its host star’s face just twice, researchers said.
Kepler-421b circles its parent star, which is cooler and dimmer than Earth’s sun, at an average distance of 100 million miles (160 million kilometers), researchers said. This places the exoplanet beyond its solar system’s “snow line” — the boundary between rocky and gaseous planets. (Beyond the snow line, ice grains glom together to form gas giants, such as Jupiter and Saturn.)
Gaseous planets often don’t remain beyond the snow line, however. Astronomers have discovered many “hot Jupiters” — giant worlds that have migrated inward significantly over time and now complete an orbit in just a few days (or, in some cases, a matter of hours).
In fact, Kepler-421b’s lack of movement makes it remarkable, Kipping said.
“This is the first example of a potentially nonmigrating gas giant in a transiting system that we’ve found,” he said.
It’s a time of amazing discovery in the hunt for planets in other solar systems. Over the past six months, more than 700 exoplanets have been found. It seems that each week brings the announcement of another foreign world: a rocky orb that seems much like Earth except that it’s 17 times more massive; a colossal planet that orbits its star at a whopping 2,000 times the distance between Earth and our sun; an Earth-like planet in a two-sun system.
On July 9, three astrophysicists — Zachory Berta-Thompson, Bruce Macintosh and Marie-Eve Naud — came together to discuss this explosion in exoplanet discovery in a live webcast hosted by The Kavli Foundation, part of a continuing series that gives viewers a chance to ask questions of scientists at the forefront of some of the world’s most exciting research.
“What is really fascinating at this stage of exoplanet science is that we have many methods, and all the methods can help to find given planets — planets with certain characteristics — and bring different information,” said Naud, a University of Montreal Ph.D. student who led a recent study that discovered a strange gas giant exoplanet called GU Pisces b. “When we are able to combine different methods, we are able to see so much more.”
Combining planet-hunting methods has not only enabled the recent explosion in exoplanet discovery , but has also increased what can be inferred about each planet. Scientists are now able to determine an exoplanet’s characteristics including its size, mass and density, as well as the chemical make-up of the planet and its atmosphere.
What’s especially exciting about identifying these chemicals is that they “can tell you things like the history of the planet — how it formed,” said Macintosh, a member of the Kavli Institute for Particle Astrophysics and Cosmology and the principal investigator for the Gemini Planet Imager. “We think we understand enough about the process that formed planets in our solar system to see that it left a chemical signature in the atmosphere of, say, Jupiter and we can try to look for that same chemical signature in the atmosphere of other planets.”
All three scientists agreed that, in addition to finding and characterizing planets, there’s another burning question that makes them excited to come to work each day: the hunt for planets that could support life.
“I think it’ll be really tough, but … thanks to the Kepler mission , we now know that the rate of occurrence of potentially habitable planets around small stars is … more than one out of ten,” said Berta-Thompson, the Torres Fellow for Exoplanetary Research at the MIT Kavli Institute for Astrophysics and Space Research. “And so this does really increase our chances.”
For more on the three astrophysicists’ expectations for finding life on other planets, their favorite of the 1700 planets discovered so far, and the burning questions that makes it exciting from them to come to work each morning, watch the complete discussion, recorded live during a Google Hangout.
While NASA’s James Webb Space Telescope (JWST) — which is scheduled to launch in 2018 — will be capable of finding signs of life on nearby exoplanets, a broad and bona fide hunt for life beyond Earth’s neighborhood will require bigger spacecraft that aren’t even on the agency’s books yet, experts say.
“To find evidence of actual life is going to take another generation of telescopes,” JWST telescope scientist Matt Mountain, director of the Space Telescope Science Institute in Baltimore, said during a NASA briefing Monday (July 14). “And to do that, we’re going to need new rockets, new approaches to getting into space, new approaches to large telescopes — highly advanced optical systems.”
A chance to find signs of life
The $8.8 billion JWST features 18 hexagonal mirror segments that will work together to form one 21-foot-wide (6.5 meters) mirror — larger than any other mirror that’s ever flown in space, NASA officials said. (For comparison, the agency’s iconic Hubble Space Telescope sports an 8-foot, or 2.4 m, primary mirror.)
JWST is optimized to view in infrared light. The telescope should be able to do lots of different things during its operational life, researchers say, including scanning the atmospheres of alien planets for oxygen and other gases that could be produced by living organisms. (Such delicate work is best performed by space telescopes, which don’t have to look through Earth’s atmosphere.)
JWST will work in concert with another NASA space mission in this regard, performing follow-up observations on promising nearby worlds found by the agency’s Transiting Exoplanet Survey Satellite (TESS), which is scheduled to blast off in 2017.
“With the James Webb, we have our first chance — our first capability of finding signs of life on another planet,” MIT astrophysicist Sara Seager said during Monday’s NASA briefing. “Now nature just has to provide for us.” [5 Bold Claims of Alien Life]
A numbers game
But nature may not be so willing, at least during the JWST mission, Seager and other experts stress. And it all comes down to numbers.
There is no shortage of planets in the Milky Way. Our galaxy teems with at least 100 billion planets, 10 to 20 percent of which, Mountain said, likely circle in their host star’s “habitable zone” — that just-right range of distances that could allow liquid water to exist on a world’s surface. If there’s nothing terribly special about Earth, then life should be common throughout the cosmos, many scientists think.
But most exoplanets are very far away, and all of them are faint. JWST, while large by current standards, won’t have enough light-collecting area to investigate more than a handful of potentially habitable planets, researchers say.
A spacecraft with a 33-foot (10 m) mirror would give researchers a much better chance of finding biosignatures in alien atmospheres, but Mountain would like something even bigger.
“With a 20-meter telescope, we can see hundreds of Earth-like planets around other stars,” he said. “That’s what it takes to find life.”
Laying the foundation
There are no concrete plans to build and launch such a large space telescope, whose size would pose a number of logistical and engineering challenges. However, JWST is a potentially big step along the way to this goal.
For example, the JWST team figured out how to make mirror segments with incredible precision — a skill that could come in handy down the road.
“They’re basically perfect,” said JWST senior project scientist John Mather of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who won a Nobel Prize in 2006 for his work with the agency’s Cosmic Background Explorer satellite.
“If we were to expand the mirror to the size of the continental United States, the mirror would be accurate to within 3 inches,” Mather said. “This is completely amazing technology we have now mastered and are using.”
The hunt for life on distant worlds will be a multi-generational effort that goes from TESS and JWST to other, larger space telescopes, Seager said. And overcoming the various challenges involved will almost certainly require the cooperation of a number of different countries and organizations.
“Putting together the partnership that can find Earth 2.0 is a challenge worthy of a great generation,” Mountain said.
Closer to home
All of this does not necessarily mean, however, that alien life won’t be detected until humanity launches an enormous space telescope. Indeed, confirmation that Earthlings aren’t alone in the universe may come from worlds much closer to home.
For example, NASA’s next Red Planet rover, which is due to launch in 2020, will hunt for signs of past Mars life. And both NASA and the European Space Agency have plans to mount a mission to Jupiter’s ocean-harboring moon Europa, which many experts regard as the solar system’s best best to host alien life.
Europe’s JUpiter ICy moons Explorer (JUICE) mission is currently scheduled to blast off in 2022 to study the Jovian satellites Callisto and Ganymede in addition to Europa. NASA officials have said they hope to launch a Europa mission sometime in the mid-2020s.
New data collected by NASA’s Voyager 1 spacecraft have helped scientists confirm that the far-flung probe is indeed cruising through interstellar space, the researchers say.
Voyager 1 made headlines around the world last year when mission scientists announced that the probe had apparently left the heliosphere — the huge bubble of charged particles and magnetic fields surrounding the sun — in August 2012.
They came to this conclusion after analyzing measurements Voyager 1 made in the wake of a powerful solar eruption known as a coronal mass ejection, or CME. The shock wave from this CME caused the particles around Voyager 1 to vibrate substantially, allowing mission scientists to calculate the density of the probe’s surroundings (because denser plasma oscillates faster.) [Photo Timeline: Voyager 1's Trek to Interstellar Space]
This density was much higher than that observed in the outer layers of the heliosphere, allowing team members to conclude that Voyager 1 had entered a new cosmic realm. (Interstellar space is emptier than areas near Earth, but the solar system thins out dramatically near the heliosphere’s edge.)
The CME in question erupted in March 2012, and its shock wave reached Voyager 1 in April 2013. After these data came in, the team dug up another, much smaller CME-shock event from late 2012 that had initially gone unnoticed. By combining these separate measurements with knowledge of Voyager 1′s cruising speed, the researchers were able to trace the probe’s entry into interstellar space to August 2012.
And now mission scientists have confirmation, in the form of data from a third CME shock, which Voyager 1 observed in March of this year, NASA officials announced Monday (July 7).
“We’re excited to analyze these new data,” Don Gurnett of the University of Iowa, the principal investigator of Voyager 1′s plasma wave instrument, said in a statement. “So far, we can say that it confirms we are in interstellar space.”
Interstellar space begins where the heliosphere ends. But by some measures, Voyager 1 remains inside the solar system, which is surrounded by a shell of comets known as the Oort Cloud.
While it’s unclear exactly how far away from Earth the Oort Cloud lies, Voyager 1 won’t get there for quite a while. NASA scientists have estimated that Voyager 1 will emerge from the Oort Cloud in 14,000 to 28,000 years.
The craft launched in September 1977, about two weeks after its twin, Voyager 2. The probes embarked upon a “grand tour” of the outer solar system, giving the world some its first good looks at Jupiter, Saturn, Uranus, Neptune and the moons of these planets.
Like Voyager 1, Voyager 2 is still active and operational. It took a different route through the solar system and is expected to follow its twin into interstellar space a few years from now.
NASA’s hobbled Kepler spacecraft is once again seeking out strange new worlds under a new 80-day mission to hunt for alien planets.
NASA officials recently approved the new Kepler spacecraft mission (called K2) after the exoplanet-hunting space probe suffered a major malfunction last year. Two of Kepler’s reaction wheels, which are used to keep the spacecraft precisely pointed in its orbit, failed, effectively ending the telescope’s mission. Now, scientists are still using the spacecraft to search for distant worlds, albeit in a different way.
“After the loss of the second reaction wheel, there were many doubters that we would ever do anything to repurpose the spacecraft,” Kepler scientist Steve Howell said during a session here at the 224th meeting of the American Astronomical Society on Tuesday (June 3). “So I’d just like to recognize people that weren’t doubters, which were many of us, that we could find something very neat to do.”
The original $600-million Kepler space telescope launched in 2009. The spacecraft’s initial four-year mission aimed to help uncover how common Earth-like planets are in the Milky Way by staring deeply into a single patch of sky. Kepler finds worlds by spotting tiny dips in the light of a star as a planet transits across the star’s face. So far, the exoplanet-hunting craft has cataloged more than 3,800 potential alien worlds, and follow-up work has confirmed about 960 of them as true planets.
Scientists think that K2 can help add to those numbers. Because K2 missions will last about 80 days, a relatively short amount of time, some scientists want to hunt for alien planets orbiting a certain class of stars that are smaller and dimmer than the sun. The new mission could target planets around these dim stars (known as M dwarfs) because the orbital period of the planet is shorter, making it easier to see in the span of 80 days.
“If you want to find nearby planets, well, you should look at nearby stars, and 70 percent of the stars locally are M dwarfs, so you’re going to look at an M dwarf,” Ben Montet, an astrophysics graduate student at the California Institute of Technology, said during the meeting. “One other benefit is that M dwarfs are everywhere.”
Kepler is now aiming itself at several pre-planned fields of sky in the plane of Earth’s orbit, called the ecliptic, for the K2 mission. The spacecraft wasn’t designed to stay in its new orbit, so engineers have been working to be sure that the probe can perform science stably. In the new orbit, solar radiation pressure helps to balance the robotic craft, but engineers still need to correct the orbit every now and then.
The new positioning also creates some interesting challenges. Astronomers using the new K2 data have to be careful of solar system objects like asteroids and planets that could sneak into the frame.
K2 just passed an engineering test showing that the newly repurposed spacecraft can still hunt for exoplanets while staying in its orbit effectively. The new mission should now be embarking on its first full, approximately 80-day science run.
NASA’s Voyager 1 and Voyager 2 spacecraft are still going strong after nearly 37 years in space.
“Both spacecraft are still operating, still very healthy. I guess as healthy as we are at the table right now,” Suzanne Dodd, the Voyager project manager at NASA’s Jet Propulsion Laboratory (JPL) said, drawing a big laugh from the audience at the SpaceFest VI conference in Pasadena, California, on May 11.
Dodd was fresh out of college in 1985 when JPL recruited her as it geared up for Voyager 2′s upcoming encounter with Uranus. Nearly 30 years later, she is project manager of the Voyager Interstellar Mission under which the two spacecraft continue to explore the vast expanse of space beyond the planets.
Voyagers of the solar system
Dodd was actually the youngster on the Voyager reunion panel. She was joined by Voyager Project Scientist Ed Stone and retired Voyager Mission Design Manager Charley Kohlhase, who were both on the project when it was in the planning stages in the early 1970s.
When the Voyagers were launched in 1977, NASA expected them to last four or five years, long enough to get them through close encounters with Jupiter and Saturn. But, they just kept going and going.
Voyager 2 went on to flybys of Uranus in 1986 and Neptune in 1989. It is now about 105 astronomical units from Earth. (One AU is the average distance between the Earth and sun, about 92 million miles.) Voyager 1, which flew out of the plane of the solar system after its 1980 flyby of Saturn, is in interstellar space at 127 AUs.
Stone and Kohlhase recalled their astonishment when an image showing two exploding volcanoes on Jupiter’s moon Io came into JPL late on a Friday afternoon in March 1979. The plumes went hundreds of miles above the surface, and the fallout covered an area the size of France.
“We had what I call a terracentric view, which was based on understanding Earth,” Stone said. “Before Voyager, the only known active volcanoes in the solar system were on Earth. Then we flew by Io, a little moon about the size of our moon, with 10 times the volcanic activity of Earth. And suddenly our terracentric extrapolation just was falling way short, and that was happening time after time after time.
“It was an incredible time where every day there were so many things we were discovering that we just moved on to the next one,” Stone added. “If we didn’t understand what we were seeing right away, we said, all right, let’s wait ’til tomorrow to see what else we get.”
A groundbreaking mission
The Voyager missions also forever changed the way spacecraft were built and operated.
“The key thing about Voyager that was a revolution was it was a totally computer-controlled spacecraft that flies itself and has fault protection on board so that if something goes wrong, it takes action,” he said. “Because now it takes us 17 and a half hours to get a command up there, and it’s 17 and a half hours before we know if anything has happened.” Before the spacecraft were launched, Kohlhase had the job of sorting through some 10,000 trajectories for projected launch windows in 1976 through 1978. He used computers to determine which ones would allow the spacecraft to make the best approaches to Jupiter, Saturn and their moons. Kohlhase and the scientists settled on 110 trajectories and ultimately used two of them.
Dodd says the Voyager mission continues to throw up challenges today. The spacecraft have 20-watt transmitters – the equivalent of a refrigerator light bulb – and signals are only 1 billionth of a billionth of a watt in strength by the time they reach Earth. JPL uses the powerful antennas of the Deep Space Network to communicate with the distant spacecraft.
“The engineering challenges are extremely unique to Voyager,” Dodd said. “You’re operating instruments below temperatures that we can’t even measure. Challenges of finding out if we turn on a component that’s next to a hydrazine line, would that hydrazine line freeze or not. We don’t know.
“Another unique challenge to it is that the engineers who built this are retired, some have passed away, you need to get people like Charley out of retirement to come and talk to us,” Dodd added. “It’s a challenge engineering-wise, it’s a challenge from a knowledge standpoint of what people know. And that’s what makes this project fun.”
The Voyagers still have a lot of life left in them even after nearly four decades on space.
“Looking forward, we expect to get 10 more years of scientific data out of the Voyager spacecraft,” Dodd said. “We basically turned off everything we can turn off to save power. Backup heaters are off, backup systems are off. We’re having some serious discussions about how to move forward, because we’re almost down to the scientific instruments now.”
After that, the spacecraft could continue on for another five to seven years sending engineering signals to Earth. Engineers are already in discussions with the Deep Space Network about what experiments could be conducted with those signals before the spacecraft fall silent.
Humanity will have the tools to detect alien life in the next two decades, but whether scientists can actually find life in another solar system depends a lot on luck, a panel of experts said Wednesday (May 21).
While the James Webb Space Telescope, expected to launch in 2018, will have the ability to search for the chemical signatures of life in the atmospheres of alien worlds, it doesn’t necessarily guarantee that scientists will find extraterrestrial life somewhere in the universe. No one is sure how life begins or how ubiquitous it is, making it very difficult to pinpoint when and where to find it, scientists said during a session here at the National Space Symposium.
“We don’t know how many planets we’re going to have to examine before we find life, and not finding it on 10 or 100 doesn’t mean it’s not there,” John Grunsfeld, NASA’s associate administrator for the science mission directorate said during the panel. “This may be very tricky.”
Scientists can stack the odds in their favor, however. Building new, bigger space telescopes could help researchers look at more stars, making the odds better that exoplanet hunters will find signs of life — like plant-produced oxygen or potentially methane — within an atmosphere.
“We can’t really tell what life is,” MIT astrophysicist and exoplanet hunter Sara Seager said. “All we can do is work with what life does. Life metabolizes and generates gasses, so that’s what we’re looking for … The good news is, whatever life is, as long as it uses chemistry, we’re all set.”
A mission still in the early stages of development could also help scientists investigate alien worlds even without the use of a large telescope. Called a “starshade,” the huge sunflower-shaped craft would block light from a star to allow a well-positioned space telescope to look at the atmospheres of rocky planets orbiting sun-like stars, a historically difficult feat.
By using the starshade, scientists can hunt for an “Earth twin” orbiting a yellow star in the habitable zone like Earth, the only planet scientists know hosts life.
“We’ll have the capability to find it [life] and we’ll have that capability within a decade with James Webb and hopefully within two decades with an Earth twin, but beyond that, it’s really just up to chance,” Seager, who is affiliated with the starshade group, said.
Life could also be lurking in our solar system, and scientists wouldn’t necessarily need a huge telescope to figure that out. NASA has started investigating a possible mission to Jupiter’s icy moon Europa to be launched sometime in the 2020s. Scientists think it’s possible that microbial life could survive in the ocean beneath the moon’s ice shell.
Finding life under Europa’s icy shell could also impact the hunt for living things outside of the solar system.
“I think it’s fair to say that we just want to see one example,” Seager said. “If we see one, we almost know that it’s everywhere because we need to be reassured, we need confidence that life is actually ubiquitous.”