This image illustrates possible ways methane might be added to Mars' atmosphere (sources) and removed from the atmosphere (sinks). NASA's Curiosity Mars rover has detected fluctuations in methane concentration in the atmosphere, implying both types of activity occur on modern Mars. Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan
NASA's Curiosity Mars rover has measured a tenfold spike in methane, an organic chemical, in the atmosphere around it and detected other organic molecules in a rock-powder sample collected by the robotic laboratory's drill.
"This temporary increase in methane, sharply up and then back down, tells us there must be some relatively localized source," said Sushil Atreya of the University of Michigan, Ann Arbor, and Curiosity rover science team.
"There are many possible sources, biological or non-biological, such as interaction of water and rock."
Researchers used Curiosity's onboard Sample Analysis at Mars (SAM) laboratory a dozen times in a 20-month period to sniff methane in the atmosphere.
During two of those months, in late 2013 and early 2014, four measurements averaged seven parts per billion.
Before and after that, readings averaged only one-tenth that level.
Curiosity also detected different Martian organic chemicals in powder drilled from a rock dubbed 'Cumberland', the first definitive detection of organics in surface materials of Mars.
These Martian organics could either have formed on Mars or been delivered to Mars by meteorites.
Organic molecules, which contain carbon and usually hydrogen, are chemical building blocks of life, although they can exist without the presence of life.
Curiosity's findings from analyzing samples of atmosphere and rock powder do not reveal whether Mars has ever harboured living microbes, but the findings do shed light on a chemically active modern Mars and on favorable conditions for life on ancient Mars.
"We will keep working on the puzzles these findings present," said John Grotzinger, Curiosity project scientist of the California Institute of Technology in Pasadena (Caltech).
"Can we learn more about the active chemistry causing such fluctuations in the amount of methane in the atmosphere? Can we choose rock targets where identifiable organics have been preserved?"
Researchers worked many months to determine whether any of the organic material detected in the Cumberland sample was truly Martian.
Curiosity's SAM lab detected in several samples some organic carbon compounds that were, in fact, transported from Earth inside the rover.
However, extensive testing and analysis yielded confidence in the detection of Martian organics.
A combined team of researchers from Japan and the U.S. has found particles of comet dust in ice extracted from the Antarctic, the first time comet dust particles have been found on the surface of the Earth.
Finding samples of material from a comet is no easy feat, sending probes to them and back is a rare occurrence.
Because of that, scientists have taken to collecting samples floating about high in the Earth's the atmosphere, an approach that has its limitations as it involves using a sticky sheet that nets few of the dust particles and which leaves oils on the samples which are further dirtied by solvents meant to clean them.
In this latest effort, the researchers drilled down approximately 58 feet into the Antarctic snow and ice at a place called Tottuki Point.
When the ice was melted back in their lab, the researchers found, among other things, extremely tiny (10 to just over 60 micrometers) dust particles which they initially believed to be meteorite dust.
Back in 2010 a team from France studying Antarctic snow reported finding what they believed to be comet particles, but this new finding is the first to report finding comet dust on the surface of the Earth.
Prior to the finding, scientists had believed that tiny dust particles would never survive the trip through the atmosphere, much less the harsh conditions once they landed.
The finding is exciting because it will mean scientists will be able to get their hands on more samples than they could with atmospheric collection.
The first ice chunks already have given up more than 40 of the dust particles.
Space scientists are eager to learn more about comets as they are believed to represent some of the oldest objects out in space, learning more about them should reveal more about the origins of our solar system, and perhaps whether they are the seeders of life on our planet, as some have come to believe.
More information: Cometary dust in Antarctic ice and snow: Past and present chondritic porous micrometeorites preserved on the Earth's surface, Earth and Planetary Science Letters, Volume 410, 15 January 2015, Pages 1–11. www.sciencedirect.com/science/… ii/S0012821X14007031
Two bodies, each of mass similar to Earth, can form a closely orbiting pair under certain conditions present during the formation of planetary systems.
This theoretical proposal is completely unlike the Earth-Moon system or Pluto-Charon, where the two bodies are very different in mass, and arises in some "kissing" collisions where two similar mass bodies encounter each other and become a bound system because of the energy lost in the strong tides raised on each other in the encounter.
The resulting binary can then persist for billions of years provided it forms well away from the central star, at half an astronomical unit (the distance between the Earth and Sun) or more.
The result does not contradict existing data for planets around other stars but suggests that future data may uncover such systems.
This is the first such study to examine the possibility of terrestrial binary planets.
During the formation of terrestrial planets, large rocky bodies orbiting around a star occasionally get close enough to interact with one another.
If two bodies collide head on or obliquely, then this interaction typically results in accretion where the two bodies merge to form a larger one, perhaps leaving behind a disk of debris from which a moon can form.
This is the standard picture for how Earth got its moon and a possible explanation for Pluto's moon, Charon.
If the two bodies collide in a grazing manner but at high velocity, then the two bodies "hit and run" and separate from one another once again, failing to form a bound pair.
The research presented today searched for a middle ground, a scenario in which the interaction results in two large bodes that do not merge but still remain locked in orbit.
This configuration, termed a terrestrial binary planetary system, would necessarily evolve into a state where the two bodies are tidally locked and with the centers of the two planets being separated by only three or so planet radii.
NB: With orbital period being almost the same as day length for both planets.
There is a good reason to believe terrestrial binary planetary systems may be possible.
In a grazing collision the angular momentum is too high to be contained within a single rotating body (it would fission) and if the bodies barely touch then they could retain their identity.
However, it requires an encounter where the bodies are initially approaching each other at low enough velocity.
Smoothed Particle Hydrodynamics represents a body as a collection of tens of thousands of particles, and it has been used to study protoplanetary collisions as well as the giant impact hypothesis of the Moon's formation.
Using SPH, collisions between two rocky Earth-sized bodies were simulated, with impact velocity and impact parameter (a measure of how head-on a collision is) being varied and the output observed.
In the cases where the bodies underwent substantial collision, the scientists replicated previous results in which a binary system did not arise but a moon might form.
However, by including interactions where the bodies are close enough to undergo a large tidal distortion, initial conditions were found that led to a terrestrial binary planetary system.
The finding of a 'cell-like' structure, which investigators now know once held water, came about as a result of collaboration between scientists in the UK and Greece.
While investigating the Martian meteorite, known as Nakhla, Dr Elias Chatzitheodoridis of the National Technical University of Athens found an unusual feature embedded deep within the rock.
In a bid to understand what it might be, he teamed up with long-time friend and collaborator Professor Ian Lyon at the University of Manchester.
Our research found that it probably wasn't a cell but that it did once hold water, water that had been heated, probably as a result of an asteroid impact."
These findings are significant because they add to increasing evidence that beneath the surface, Mars does provide all the conditions for life to have formed and evolved.
It also adds to a body of evidence suggesting that large asteroids hit Mars in the past and produce long-lasting hydrothermal fields that could sustain life on Mars, even in later epochs, if life ever emerged there.
As part of the research, the feature was imaged in unprecedented detail by Dr Sarah Haigh of The University of Manchester whose work usually involves high resolution imaging for next generation electronic devices, which are made by stacking together single atomic layers of graphene and other materials with the aim of making faster, lighter and bendable mobile phones and tablets.
A similar imaging approach was able to reveal the atomic layers of materials inside the meteorite.
Together their combined experimental approach has revealed new insights into the geological origins of this fascinating structure.
Professor Lyon said: "We have been able to show the setting is there to provide life. It's not too cold, it's not too harsh. Life as we know it, in the form of bacteria, for example, could be there, although we haven't found it yet."
"It's about piecing together the case for life on Mars, it may have existed and in some form could exist still."
Now, the team is using these and other state-of-the-art techniques to investigate new secondary materials in this meteorite and search for possible bio signatures which provide scientific evidence of life, past or present.
Professor Lyon concluded: "Before we return samples from Mars, we must examine them further, but in more delicate ways. We must carefully search for further evidence."
More information: "A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology." Elias Chatzitheodoridis, Sarah Haigh, Ian Lyon. Astrobiology. August 2014, 14(8): 651-693. online.liebertpub.com/doi/pdfp… 0.1089/ast.2013.1069
On Mercury a solar day is about 176 Earth days long. During its first Mercury solar day in orbit the MESSENGER spacecraft imaged nearly the entire surface of Mercury to generate a global monochrome map at 250 meters per pixel resolution and a 1 kilometer per pixel resolution color map. Credit: NASA/JHU APL/CIW
Mercury has an oddball orbit, it takes longer for it to rotate on its axis and complete a day than it takes to orbit the sun and complete a year.
Now, researchers suggest photosynthesis could take place on an alien planet with a similarly bizarre orbit, potentially helping support complex life.
However, the scientists noted that the threat of prolonged periods of darkness and cold on these planets would present significant challenges to life, and could even potentially freeze their atmospheres.
Astronomers have discovered more than 1,700 alien planets in the past two decades, raising the hope that at least some might be home to extraterrestrial life.
Scientists mostly focus the search for alien life on exoplanets in the habitable zones of stars.
These are regions where worlds would be warm enough to have liquid water on their surfaces, a potential boon to life.
Although many exoplanets are potentially habitable, they may differ from Earth significantly in one or more ways.
For instance, habitable planets around dim red dwarf stars orbit much closer than Earth does to the Sun, sometimes even closer than Mercury's distance.
Red dwarfs are of interest as possible habitats for life because they are the most common stars in the universe, if life can exist around red dwarfs, then life might be very common across the cosmos.
Recent findings from NASA's Kepler Space Observatory suggest that at least half of all red dwarfs host rocky planets that are one-half to four times the mass of Earth.
Since a planet in the habitable zone of a red dwarf orbits very near its star, it experiences much stronger gravitational tidal forces than Earth does from the Sun, which slows the rate at which those worlds spin.
The most likely result of this slowdown is that the planet enters what is technically called a 1:1 spin orbit resonance, completing one rotation on its axis every time it completes one orbit around its star.
This rate of rotation means that one side of that planet will always face toward its star, while the other side will permanently face away, just as the Moon always shows the same side to Earth.
One recent study suggests that such "tidally locked" planets may develop strange lobster-shaped oceans basking in the warmth of their stars on their daysides, while the nightsides of such worlds are mostly covered in an icy shell.
More information: "Photosynthetic potential of planets in 3 : 2 spin–orbit resonances." S.P. Brown, et al. International Journal of Astrobiology DOI: dx.doi.org/10.1017/S1473550414000068
A new ovoid structure discovered in the Nakhla Martian meteorite is made of nanocrystalline iron-rich clay, contains a variety of minerals, and shows evidence of undergoing a past shock event from impact, with resulting melting of the permafrost and mixing of surface and subsurface fluids.
Based on the results of a broad range of analytical studies to determine the origin of this new structure, scientists present the competing hypotheses for how this ovoid formed, point to the most likely conclusion, and discuss how these findings impact the field of astrobiology in a fascinating article published in Astrobiology.
While the authors do not believe the formation of this structure involved biological materials, that is a possible hypothesis, and they note that evidence exists supporting the presence of niche environments in the Martian subsurface that could support life.
"This study illustrates the importance of correlating different types of datasets when attempting to discern whether something in rock is a biosignature indicative of life," says Sherry L. Cady, PhD, Editor-in-Chief of Astrobiology and Chief Scientist at the Pacific Northwest National Laboratory.
"Though the authors couldn't prove definitively that the object of focus was evidence of life, their research strategy revealed a significant amount of information about the potential for life to inhabit the subsurface of Mars."
Asteroids and comets that repeatedly smashed into the early Earth covered the planet's surface with molten rock during its earliest days, but still may have left oases of water that could have supported the evolution of life, scientists say.
The new study reveals that during the planet's infancy, the surface of the Earth was a hellish environment, but perhaps not as hellish as often thought, scientists added.
Earth formed about 4.5 billion years ago. The first 500 million years of its life are known as the Hadean Eon.
Although this time amounts to more than 10 percent of Earth's history, little is known about it, since few rocks are known that are older than 3.8 billion years old.
An artistic conception of the early Earth-moon system showing the Earth's surface after being bombarded with large impacts, causing magma extrusion on the surface, though some liquid water was retained. Image released on July 30, 2014. Credit: Simone Marchi
Earth's violent youth
For much of the Hadean, Earth and its sister worlds in the inner solar system were pummeled with an extraordinary number of cosmic impacts.
"It was thought that because of these asteroids and comets flying around colliding with Earth, conditions on early Earth may have been hellish," said lead study author Simone Marchi, a planetary scientist at the Southwest Research Institute in Boulder, Colorado.
This imagined hellishness gave the eon its name, Hadean comes from the word Hades, the lord of the underworld in Greek mythology.
However, in the past dozen years or so, a radically different picture of the Hadean began to emerge.
Analysis of minerals trapped within microscopic zircon crystals dating from this eon "suggested there was liquid water on the surface of the Earth back then, clashing with the previous picture that the Hadean was hellish," Marchi said.
This could explain why the evidence of the earliest life on Earth appears during the Hadean, maybe the planet was less inhospitable during that eon than previously thought.
This artist's illustration shows a close-up of the early Earth, revealing magma extrusion on the surface and the scars from severe cosmic bombardment. Image released on July 30, 2014. Credit: Simone Marchi
Cosmic bombardment history
The exact timing and magnitude of the impacts that smashed Earth during the Hadean are unknown.
To get an idea of the effects of this bombardment, Marchi and his colleagues looked at the moon, whose heavily cratered surface helped model the battering that its close neighbour Earth must have experienced back then.
"We also looked at highly siderophile elements (elements that bind tightly to iron), such as gold, delivered to Earth as a result of these early collisions, and the amounts of these elements tells us the total mass accreted by Earth as the result of these collisions," Marchi said.
Prior research suggests these impacts probably contributed less than 0.5 percent of the Earth's present-day mass.
The researchers discovered that "the surface of the Earth during the Hadean was heavily affected by very large collisions, by impactors larger than 100 kilometers (60 miles) or so, really, really big impactors," Marchi said.
"When Earth has a collision with an object that big, that melts a large volume of the Earth's crust and mantle, covering a large fraction of the surface," Marchi added.
These findings suggest that Earth's surface was buried over and over again by large volumes of molten rock, enough to cover the surface of the Earth several times. This helps explain why so few rocks survive from the Hadean, the researchers said.
However, although these findings might suggest that the Hadean was a hellish eon, the researchers found that "there were time gaps between these large collisions," Marchi said.
"Generally speaking, there may have been something on the order of 20 or 30 impactors larger than 200 km (120 miles) across during the 500 million years of the Hadean, so the time between such impactors was relatively long," Marchi said.
Any water vapourised near these impacts "would rain down again," Marchi said, and "there may have been quiet tranquil times between collisions, there could have been liquid water on the surface."
The researchers suggested that life emerging during the Hadean was probably resistant to the high temperatures of the time.
Marchi and his colleagues detailed their findings in the July 31 issue of the journal Nature.
More Information: Widespread mixing and burial of Earth’s Hadean crust by asteroid impacts. - Authors: S. Marchi, W. F. Bottke, L. T. Elkins-Tanton, M. Bierhaus, K. Wuennemann, A. Morbidelli & D. A. Kring - doi:10.1038/nature13539
Astronomers have detected a mysterious signal 240 million light years away from Earth. The unidentified signal is a 'spike of intensity at a very specific wavelength of x-ray light', but scientists don't yet know what the origin is.
Picked up in the Perseus Cluster, one of the biggest objects in the universe, the discovery is said to be the best evidence of dark matter yet.
Astronomers believe dark matter constitutes 85 per cent of the matter in the universe, but doesn't emit or absorb light like normal matter such as protons or electrons, which are known to make up the familiar elements seen in planets, stars, and galaxies.
Researchers suggest intensity coming from the Perseus Cluster could be a signature from the decay of a 'sterile neutrino,' which are a hypothetical type of neutrino thought to interact with normal matter via gravity but while holding exciting potential, the results must be confirmed with additional data to rule out other explanations and to see whether it is plausible that dark matter has been observed.
The artist concept depicts multiple-transiting planet systems, which are stars with more than one planet. The planets eclipse or transit their host star from the vantage point of the obplanetserver. This angle is called edge-on. Credit: NASA
The newly-verified objects orbit 305 different stars, and therefore include multi-world systems that are reminiscent of the Sun's own planetary family.
The announcement of these discoveries was followed by news that Kepler had also found the first Earth-size planet in the habitable zone of its star, Kepler 186f.
This is a significant milestone in the task of determining the prevalence of terrestrial planets in the Milky Way galaxy.
"These results are showing us that not only are Earth-sized planets common, but so are multi-planet systems containing potentially habitable worlds," notes Jason Rowe, a SETI Institute astronomer who co-led the study.
"Most of the new planets orbit their host star much closer than Mercury, but a few are beginning to bear a similarity to our own solar system."
The deluge of new planets has been intensified by a new analysis scheme called verification by multiplicity.
This technique can be applied to many planets at once, allowing the researchers to verify hundreds of new planetary systems in wholesale fashion, rather than teasing them from the Kepler data one-by-one as done in the past.
The new technique uses probability arguments based on the recognition that, of the 150,000 stars observed by Kepler, hundreds were found that have multiple planet candidates.
On this basis, the researchers are assured that their results are not distorted by binary stars that can mimic a multi-world system.
The new discoveries increase the total number of known exoplanets to over 1,700.
"From this work we've also learned that planets in these multiple systems are small, and their orbits are flat and circular, much like our own solar system," Rowe said.
On April 17th, the Kepler team announced the discovery of Kepler 186f, the first Earth-sized planet found in the habitable zone of its host star, marking a major milestone in determining the frequency of Earth-like planets in the Milky Way galaxy.
"Uncovering these worlds and showing that habitable worlds could be very common has increased the likelihood that there is life, perhaps abundant life, elsewhere in the cosmos," notes David Black, President and CEO of the SETI Institute.
Data collection from the Kepler mission ended in the spring of last year, due to the failure of a second on-board reaction wheel, essential to accurate pointing of the telescope.
However, on May 20th, NASA announced the approval of the K2 mission, intended to repurpose Kepler to use the pressure of sunlight hitting the side of the spacecraft to act as a third wheel.
"We can't continue to look at the original Kepler star field," said Douglas Caldwell, Kepler Instrument Scientist at the SETI Institute, "but spacecraft are built and operated by very smart people, and thanks to the hard work of the entire Kepler team we can now search for planets in a wide variety of environments and conditions, including star forming regions. Doing so will teach us more about how our own planetary system formed and evolved."
"The more we explore the more we find worlds among the stars that remind us of home," Rowe notes.
More information: Jason Rowe is presenting these results at this week's annual meeting of the Canadian Astronomical Society (CASCA) in Quebec: casca2014.craq-astro.ca/index_en.php
This artist's conception shows a hypothetical alien world orbiting a red dwarf star. Although it is in the star’s habitable zone, this planet faces an extreme space environment that is stripping its atmosphere and generating powerful aurorae. Since they are subjected to such harsh physical conditions, red-dwarf planets may not be habitable after all, so life in the universe might be even rarer than we thought. Credit: Harvard-Smithsonian Center for Astrophysics (CfA)
Life in the universe might be even rarer than we thought. Recently, astronomers looking for potentially habitable worlds have targeted red dwarf stars because they are the most common type of star, comprising 80 percent of the stars in the universe.
But a new study shows that harsh space weather might strip the atmosphere of any rocky planet orbiting in a red dwarf's habitable zone.
Earth is protected from solar eruptions and space weather by its magnetic field. Just like the shields of the Starship Enterprise, Earth's magnetic field deflects incoming energy blasts.
We also are protected by distance since Earth orbits 93 million miles from the Sun.
Red dwarf stars are smaller and cooler than the Sun. To be in the star's habitable zone, where the temperature is warm enough for liquid water, a planet would have to be much closer to its star than the Earth is to the Sun. As a result, such a planet would be subjected to severe space weather.
Previous work has looked at the impact of stellar flares from a red dwarf on a nearby planet. In contrast, the new research examines the effect of the red dwarf's constantly blowing stellar wind.
The team used a computer model developed at the University of Michigan to represent three known red-dwarf planets circling a simulated, middle-aged red dwarf.
They found that even an Earth-like magnetic field could not necessarily protect a habitable-zone world from the star's continuous bombardment.
Although there were moments when the planet's magnetic shields held firm, it spent far more time with weak shields than strong shields.
"The space environment of close-in exoplanets is much more extreme than what the Earth faces," explains co-author Jeremy Drake (CfA).
"The ultimate consequence is that any planet potentially would have its atmosphere stripped over time."
The extreme space weather also would trigger spectacular aurorae, or Northern Lights. The aurora on a red-dwarf planet could be 100,000 times stronger than those on Earth, and extend from the poles halfway to the equator.
"If Earth were orbiting a red dwarf, then people in Boston would get to see the Northern Lights every night," adds Cohen.
"Oh the other hand, we'd also be in constant darkness because of tidal locking, and blasted by hurricane-force winds because of the dayside-nightside temperature contrast. I don't think even hardy New Englanders want to face that kind of weather."
Cassini mission scientist Carolyn Porco talks about her life and experiences as a Saturn explorer.
This interview, in which Porco discusses her fascination with astronomy and planets, and how that fascination led her down her remarkable career path, was conducted by space historian Andrew Chalkin, and it is just so wonderful to watch.
Porco's love of scientific investigation and passion for what she does is so compelling, it's hard not to get lost in her stories of coming up in the Bronx, her accounts of past missions, and her continued enthusiasm for the science that she and the Cassini team are busy conducting to this day.
Arsia Mons, the third-largest volcano on Mars may have been home to a habitable environment in Mars's relatively recent past. The rippled terrain in the foreground shows where a glacier once clung to the foothills of the mountain. Brown University researchers show that eruptions occurred under that ice sheet, which would have created lakes of liquid water. Where there was water, there's the possibility of past life. (Colours indicate elevation.)
Credit: NASA /Goddard Space Flight Center /Arizona State University /Brown University
Heat from a volcano erupting beneath an immense glacier would have created large lakes of liquid water on Mars in the relatively recent past, and where there's water, there is also the possibility of life.
The slopes of a giant Martian volcano, once covered in glacial ice, may have been home to one of the most recent habitable environments yet found on the Red Planet, according to new research led by Brown University geologists.
Nearly twice as tall as Mount Everest, Arsia Mons is the third tallest volcano on Mars and one of the largest mountains in the solar system.
This new analysis of the landforms surrounding Arsia Mons shows that eruptions along the volcano's northwest flank happened at the same time that a glacier covered the region around 210 million years ago.
The heat from those eruptions would have melted massive amounts of ice to form englacial lakes, bodies of water that form within glaciers like liquid bubbles in a half-frozen ice cube.
The ice-covered lakes of Arsia Mons would have held hundreds of cubic kilometers of meltwater, according to calculations by Kat Scanlon, a graduate student at Brown who led the work, and where there's water, there's the possibility of a habitable environment.
"This is interesting because it's a way to get a lot of liquid water very recently on Mars," Scanlon said.
While 210 million years ago might not sound terribly recent, the Arsia Mons site is much younger than the habitable environments turned up by Curiosity and other Mars rovers.
Those sites are all likely older than 2.5 billion years. The fact that the Arsia Mons site is relatively young makes it an interesting target for possible future exploration.
"If signs of past life are ever found at those older sites, then Arsia Mons would be the next place I would want to go," Scanlon said.
That view got a big boost in 2003 when Brown geologist Jim Head and David Marchant at Boston University, showed that terrain around Arsia Mons looks strikingly similar to landforms left by receding glaciers in the Dry Valleys of Antarctica.
Parallel ridges toward the bottom of the mountain appear to be drop moraines, piles of rubble deposited at the edges of a receding glacier.
An assemblage of small hills in the region also appears to be debris left behind by slowly flowing glacial ice.
The glacier idea got another boost with recently developed climate models for Mars that take into account changes in the planet's axis tilt.
The models suggested that during periods of increased tilt, ice now found at the poles would have migrated toward the equator.
That would make Mars's giant mid-latitude mountains; Ascraeus Mons, Pavonis Mons and Arsia Mons, prime locations for glaciation around 210 million years ago.
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 (JWST), 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 at the 30th US National Space Symposium in Clorado.
"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."
This diagram shows the position of Kepler-186f in relation to Earth. Credit: NASA Ames/SETI Institute/JPL-CalTech
A mission still in the early stages of development could also help scientists investigate alien worlds even without the use of a large telescope.
"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.
The project is led by Jeremy Kasdin, a professor at Princeton University, N.J., in conjunction with JPL and support from Northrop Grumman of Redondo Beach, Calif.
The artist's concept depicts Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone, a range of distances from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth. The artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant worlds. Credit: Danielle Futselaar.
The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory.
The initial discovery, made by NASA's Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes.
It also confirms that Earth-sized planets do exist in the habitable zone of other stars.
"What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form," says Elisa Quintana of the SETI Institute and NASA Ames Research Center who led the paper published in the current issue of the journal Science.
The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.
Steve Howell, Kepler's Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot an exoplanet of this size and proximity to its host star.
"However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option."
With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected.
To do this, the team obtained extremely high spatial resolution observations from the eight-meter Gemini North telescope on Mauna Kea in Hawai`i using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-meter Keck II telescope, Gemini's neighbour on Mauna Kea.
Together, these data allowed the team to rule out sources close enough to the star's line-of-sight to confound the Kepler evidence, and conclude that Kepler's detected signal has to be from a small planet transiting its host star.
The diagram compares the planets of the inner solar system to Kepler-186, a five-planet system about 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 orbit a star classified as a M1 dwarf, measuring half the size and mass of the sun. The Kepler-186 system is home to Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distances from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth. Kepler-186f is less than ten percent larger than Earth in size, but its mass and composition are not known. Kepler-186f orbits its star once every 130-days and receives one-third the heat energy that Earth does from the sun, placing it near the outer edge of the habitable zone. The inner four companion planets all measure less than fifty percent the size of Earth. Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e, orbit every three, seven, 13, and 22 days, respectively, making them very hot and inhospitable for life as we know it. The Kepler space telescope, which simultaneously and continuously measured the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun. Kepler does not directly image the planets it detects. The space telescope infers their existence by the amount of starlight blocked when the orbiting planet passes in front of a distant star from the vantage point of the observer. The artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant Credit: Credit: NASA Ames/SETI Institute/JPL-CalTech.
Tilted orbits such as those shown might make some planets wobble like a top that’s almost done spinning, an effect that could maintain liquid water on the surface, thus giving life a chance. Credit: NASA
A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, sometimes it helps.
That's because such "tilt-a-worlds," as astronomers sometimes call them, turned from their orbital plane by the influence of companion planets, are less likely than fixed-spin planets to freeze over, as heat from their host star is more evenly distributed.
This happens only at the outer edge of a star's habitable zone, the swath of space around it where rocky worlds could maintain liquid water at their surface, a necessary condition for life.
Further out, a "snowball state" of global ice becomes inevitable, and life impossible.
The findings, which are published online and will appear in the April issue of Astrobiology, have the effect of expanding that perceived habitable zone by 10 to 20 percent.
And that in turn dramatically increases the number of worlds considered potentially right for life.
Such a tilt-a-world becomes potentially habitable because its spin would cause poles to occasionally point toward the host star, causing ice caps to quickly melt.
Barnes is second author on the paper. First author is John Armstrong of Weber State, who earned his doctorate at the UW.
Earth and its neighbour planets occupy roughly the same plane in space. But there is evidence, Barnes said, of systems whose planets ride along at angles to each other.
As such, "they can tug on each other from above or below, changing their poles' direction compared to the host star."
The team used computer simulations to reproduce such off-kilter planetary alignments, wondering, he said, "what an Earthlike planet might do if it had similar neighbours."
Their findings also argue against the long-held view among astronomers and astrobiologists that a planet needs the stabilizing influence of a large moon, as Earth has, to have a chance at hosting life.
"We're finding that planets don't have to have a stable tilt to be habitable," Barnes said. Minus the moon, he said, Earth's tilt, now at a fairly stable 23.5 degrees, might increase by 10 degrees or so. Climates might fluctuate, but life would still be possible.
"This study suggests the presence of a large moon might inhibit life, at least at the edge of the habitable zone."
The work was done through the UW's Virtual Planetary Laboratory, an interdisciplinary research group that studies how to determine if exoplanets—those outside the solar system—might have the potential for life.
"The research involved orbital dynamics, planetary dynamics and climate studies. It's bigger than any of those disciplines on their own," Barnes said.
Armstrong said that expanding the habitable zone might almost double the number of potentially habitable planets in the galaxy.
Applying the research and its expanded habitable zone to our own celestial neighborhood for context, he said, "It would give the ability to put Earth, say, past the orbit of Mars and still be habitable at least some of the time, and that's a lot of real estate." More information: Paper: online.liebertpub.com/doi/abs/10.1089/ast.2013.1129
Cold and dry today, Mars was previously warm and wet but possibly only at intervals, a study published on Sunday suggests.
Scientists have long puzzled over what happened to the water, the precious stuff of life, on the Red Planet.
Unmanned spacecraft have sent home tantalising images of gouged canyons, valleys and sedimentary deltas, while landers have found hydrous rocks, all suggesting Mars at one time hosted hundreds of kilometres (miles) of rivers and lakes.
Today, though, Mars is too cold and the pressure of its carbon-dioxide atmosphere way too low for liquid H2O to exist. If you tried to pour water on its surface, it would simultaneously freeze and vapourise.
So when did Mars host liquid water? And what happened to it?
In a study published in the journal Nature Geoscience, planetary geologist Edwin Kite of the California Institute of Technology takes a new stab at the riddle.
Kite and his team measured craters, left on the Martian surface by asteroid collisions, to gain an idea of its past atmospheric pressure.
The principle behind their calculation is this: the thicker the atmosphere, the bigger the space rock has to be to survive the friction of contact with it.
Conversely, a thinner atmosphere means that smaller rocks are able to survive the descent and whack the surface.
Kite's team looked at 319 craters in Aeolis Dorsa, a 3.6-billion-year-old region that shows evidence of past rivers to get an indication.
Mystery of flowing water
They calculated that these craters were formed when Mars had atmospheric pressure of up to 0.9 bar.
This pressure is 150 times greater than that of today and intriguingly close to that of the water-rich Planet Earth at sea level.
The bad news, though, is that Mars is far more distant from the Sun than Earth and at that far-off time, our star was much less bright than now.
As a result, Mars would have required pressures of at least five bar for its surface to keep above the freezing point of water. It seems to have lacked a long-lasting thick atmosphere during its river period.
"If Mars did not have a stable multi-bar atmosphere at the time that the rivers were flowing—as suggested by our results—then a warm and wet CO2/H2O greenhouse is ruled out, and long-term average temperatures were most likely below freezing," said the study.
This throws up other possible explanations for the water, said Sanjoy Som of NASA Ames Research Center in a commentary published in the same journal.
One is that the water was high in acidity and salt content, giving it a lower freezing point and enabling it survive as a liquid in lower air pressure.
Another is that greenhouse gases from volcanic eruptions helped Mars, for a while, to have a denser atmosphere that enabled the water to flow.
Another possibility is "transient intervals" of denser atmosphere caused by the planet's tilt, said Som.
Like a child's top that is slightly off centre, Mars tilts slowly around its axis of spin.
It takes 120,000 years to complete one axial revolution, a timescale that leads to major changes in the amount of sunlight reaching its poles, whose water either froze to form ice-sheets or warmed to "reinflate" the atmosphere and form rivers that flowed at kinder times.
More information: Nature paper: Low palaeopressure of the martian atmosphere estimated from the size distribution of ancient craters, www.nature.com
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