Posted on by Fraser Cain

Galaxies Could Be Twice as Large as Previously Estimated

A wide-field view of NGC 300. Image credit: AAO-David Malin/Gemini Observatory. Click to enlarge
Like archaeologists unearthing a ‘lost city,’ astronomers using the 8-meter Gemini South telescope have revealed that the galaxy NGC 300 has a large, faint extended disk made of ancient stars, enlarging the known diameter of the galaxy by a factor of two or more.

The finding also implies that our own Milky Way Galaxy could be much larger than current textbooks say. Scientists will also need to explain the mystery of how galaxies like NGC 300 can form with stars so far from their centers.

The research, by an Australian and American team of scientists was just published in the August 10, 2005 issue of the Astrophysical Journal.

The team used the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile, and were able to clearly resolve extremely faint stars in the disk up to 47,000 light-years from the galaxy?s center?double the previously known radius of the disk. To detect these stars, images were obtained that went more than ten times ?deeper? than any previous images of this galaxy (Figure 1).

?A few billion years ago the outskirts of NGC 300 were brightly lit suburbs that would have shown up as clearly as its inner metropolis,? said the paper?s lead author, Professor Joss Bland-Hawthorn of the Anglo-Australian Observatory in Sydney, Australia. ?But the suburbs have dimmed with time, and are now inhabited only by faint, old stars?stars that need large telescopes such as Gemini South to detect them.?

The finding has profound implications for our own galaxy since most current estimates put the size of our Milky Way at about 100,000 light-years or about the size now estimated for NGC 300. ?However, the galaxy is much more massive and brighter than NGC 300 so on this basis, our galaxy is also probably much larger than we previously thought?perhaps as much as 200,000 light-years across,? said Bland-Hawthorn.

The Galaxy That Keeps On Keeping On!

Adding to these compelling findings is the fact that the team found no evidence for truncating, or an abrupt ?cutting-off’ of the star population as seen in many galaxies further from the central regions.

Team member Professor Bruce Draine of Princeton University explains: “It’s hard to understand how such an extensive stellar disk that falls off so smoothly in density could have formed ? this is really a huge surprise to us. Because it takes an incredibly long time to evenly disperse stars from a galaxy’s central disk to these extreme distances, it seems more likely that we are seeing the results of star formation that took place long ago, perhaps as much as ten billion years ago.”

?We now realize that there are distinctly different types of galaxy disks,? said team member Professor Ken Freeman of the Research School of Astronomy and Astrophysics at the Australian National University. ?Probably most galaxies are truncated?the density of stars in the disk drops off sharply. But NGC 300 just seems to go on forever. The density of stars in the disk falls off very smoothly and gradually.?

The observers traced NGC 300?s disk out to the point where the surface density of stars was equivalent to a one-thousandth of a sun per square light-year. ?This is the most extended and diffuse population of stars ever seen,? said Bland-Hawthorn.

NGC 300 is a spiral member of the Sculptor group of galaxies, the closest extragalactic cluster to us, and is about 6.1 million light-years away. Most of its stars lie in a fairly flat disk making it appear to be a very normal spiral galaxy like our Milky Way. NGC 300 is the first galaxy outside of our Local Group to be studied to this depth. There have only been two others studied to such faint levels, the Andromeda galaxy and its neighbor M33, both in our Local Group (see adjacent background information box).

The researchers have been granted more time on Gemini South to determine exactly what kind of stars they are seeing in the outskirts of NGC 300, and to make similar studies of other galaxies.

?We still have a lot to learn about how galaxies like ours formed,? said Bland-Hawthorn. ?Our next Gemini observations, that we have planned for later this year, should provide even more important clues and hopefully even more surprises!?

Original Source: Gemini Observatory

Posted on by Fraser Cain

Zo? Heads Back to the Desert to Search for Life

Zo?, an autonomous solar-powered rover. Image credit: NASA Click to enlarge
Carnegie Mellon University researchers and their colleagues from NASA’s Ames Research Center, the universities of Tennessee, Arizona and Iowa, as well as Chilean researchers at Universidad Catolica del Norte (Antofagasta) are preparing for the final stage of a three-year project to develop a prototype robotic astrobiologist, a robot that can explore and study life in the driest desert on Earth.

The team will direct and monitor Zo?, an autonomous solar-powered rover developed at Carnegie Mellon, as it travels 180 kilometers in Chile’s Atacama Desert. Zo? is equipped with scientific instruments to seek and identify micro-organisms and to characterize their habitats. It will use them as it explores three diverse regions of the desert during its two-month stay, which runs from August 22 to October 22.

The results of this expedition ultimately may enable future robots to seek life on Mars, as well as enabling the discovery of new information about the distribution of life on Earth.

The search-for-life project was begun in 2003 under NASA’s Astrobiology Science and Technology Program for Exploring Planets, or ASTEP, which concentrates on pushing the limits of technology to study life in harsh environments.

Zo?’s abilities represent the culmination of three years of work to determine the optimum design, software and instrumentation for a robot that can autonomously investigate different habitats. During the 2004 field season, Zo? exceeded scientists’ expectations when it traveled 55 kilometers autonomously and detected living organisms using its onboard Fluorescence Imager (FI) to locate chlorophyll and other organic molecules.

“Our goal with this final investigation is to develop a method to create a real-time, 3D topographic ‘map’ of life at the microscopic level,” said Nathalie Cabrol, a planetary scientist at NASA Ames and the SETI Institute who heads the science investigation aspects of the project. “This map eventually could be integrated with satellite data to create an unprecedented tool for studies of large-scale environmental activities on life in specific areas. This concept can be applied to planetary research and also on Earth to explore other extreme environments.”

“This is the first time a robot is looking for life,” said Carnegie Mellon associate research professor David Wettergreen, who leads the project. “We have worked with rovers and individual instruments before, but Zo? is a complete system for life seeking. We are working toward full autonomy of each day’s activities, including scheduling time and resource use, control of instrument deployment and navigation between study areas.

“Last year we learned that the Fluorescence Imager can detect organisms in this environment. This year we’ll be able to see how densely an area is populated with organisms and map their distribution. We intend to have the robot make as many as 100 observations and make advances in procedural developments like how to decide where to explore.”

Zo? will visit a foggy coastal region, the dry Andean altiplano, and an area in the desert’s arid interior that receives no precipitation for decades at a time. At these sites, the rover’s activities will be guided remotely from an operations center in Pittsburgh where the researchers will characterize the environment, seek clear proof of life and map the distribution of various habitats. During last year’s mission, the team carried out experiments using an imager able to detect fluorescence in an area underneath the rover. The FI detects signals from two fluorescent dyes that mark carbohydrates and proteins ? as well as the natural fluorescence of chlorophyll. The FI, developed by Alan Waggoner, director of the university’s Molecular Biosensor and Imaging Center (MBIC), was not fully automated last year. Scientists had to follow the rover and spray dyes onto the sample area. This year, Zo? can spray a mixture of dyes for DNA, protein, lipid and carbohydrates without human intervention.

The Life in the Atacama project is funded with a $3 million, three-year grant from NASA to Carnegie Mellon’s Robotics Institute in the School of Computer Science. They collaborate with MBIC scientists, who received a separate $900,000 NASA grant to develop fluorescent dyes and automated microscopes to locate various forms of life.

The science team uses EventScope, a remote experience browser developed by researchers at the STUDIO for Creative Inquiry in Carnegie Mellon’s College of Fine Arts, to guide Zo?. It enables scientists and the public to experience the Atacama environment through the rover’s “eyes” and various sensors. During the field investigation, scientists will interact with Zo? in a science operations control room at the Remote Experience and Learning Lab in Pittsburgh. Scientists from NASA, the Jet Propulsion Laboratory, the University of Tennessee, University of Arizona, the British Antarctic Survey and the European Space Agency will participate.

For more information, images and field reports from the Atacama, visit: www.frc.ri.cmu.edu/atacama.

Original Source: Carnegie Mellon News Release

Posted on by Fraser Cain

Triple Asteroid System Discovered

Orbits of twin moonlets around 87 Sylvia. Image credit: ESO Click to enlarge
One of the thousands of minor planets orbiting the Sun has been found to have its own mini planetary system. Astronomer Franck Marchis (University of California, Berkeley, USA) and his colleagues at the Observatoire de Paris (France) have discovered the first triple asteroid system – two small asteroids orbiting a larger one known since 1866 as 87 Sylvia.

“Since double asteroids seem to be common, people have been looking for multiple asteroid systems for a long time,” said Marchis. “I couldn’t believe we found one.”

The discovery was made with Yepun, one of ESO’s 8.2-m telescopes of the Very Large Telescope Array at Cerro Paranal (Chile), using the outstanding image’ sharpness provided by the adaptive optics NACO instrument. Via the observatory’s proven “Service Observing Mode”, Marchis and his colleagues were able to obtain sky images of many asteroids over a six-month period without actually having to travel to Chile.

One of these asteroids was 87 Sylvia, which was known to be double since 2001, from observations made by Mike Brown and Jean-Luc Margot with the Keck telescope. The astronomers used NACO to observe Sylvia on 27 occasions, over a two-month period. On each of the images, the known small companion was seen, allowing Marchis and his colleagues to precisely compute its orbit. But on 12 of the images, the astronomers also found a closer and smaller companion. 87 Sylvia is thus not double but triple!

Because 87 Sylvia was named after Rhea Sylvia, the mythical mother of the founders of Rome, Marchis proposed naming the twin moons after those founders: Romulus and Remus. The International Astronomical Union approved the names.

Sylvia’s moons are considerably smaller, orbiting in nearly circular orbits and in the same plane and direction. The closest and newly discovered moonlet, orbiting about 710 km from Sylvia, is Remus, a body only 7 km across and circling Sylvia every 33 hours. The second, Romulus, orbits at about 1360 km in 87.6 hours and measures about 18 km across.

The asteroid 87 Sylvia is one of the largest known from the asteroid main belt, and is located about 3.5 times further away from the Sun than the Earth, between the orbits of Mars and Jupiter. The wealth of details provided by the NACO images show that 87 Sylvia is shaped like a lumpy potato, measuring 380 x 260 x 230 km. It is spinning at a rapid rate, once every 5 hours and 11 minutes.

The observations of the moonlets’ orbits allow the astronomers to precisely calculate the mass and density of Sylvia. With a density only 20% higher than the density of water, it is likely composed of water ice and rubble from a primordial asteroid. “It could be up to 60 percent empty space,” said co-discoverer Daniel Hestroffer (Observatoire de Paris, France).

“It is most probably a “rubble-pile” asteroid”, Marchis added. These asteroids are loose aggregations of rock, presumably the result of a collision. Two asteroids smacked into each other and got disrupted. The new rubble-pile asteroid formed later by accumulation of large fragments while the moonlets are probably debris left over from the collision that were captured by the newly formed asteroid and eventually settled into orbits around it. “Because of the way they form, we expect to see more multiple asteroid systems like this.”

Marchis and his colleagues will report their discovery in the August 11 issue of the journal Nature, simultaneously with an announcement that day at the Asteroid Comet Meteor conference in Arma??o dos B?zios, Rio de Janeiro state, Brazil.

Original Source: ESO News Release

Posted on by Fraser Cain

NASA Celebrates Discovery’s Return

Discovery resting on the runway at Edwards Air Force Base. Image credit: NASA Click to enlarge
The Space Shuttle Discovery is home after a 14-day, 5.8 million-mile journey in space. The mission included breathtaking in-orbit maneuvers, tests of new equipment and procedures, a first-of-its-kind spacewalking repair, and virtual visits with two heads of state.

Commander Eileen Collins and the crew of the STS-114 mission, Jim Kelly, Charlie Camarda, Wendy Lawrence, Steve Robinson, Andy Thomas and Soichi Noguchi of Japan, landed at Edwards Air Force Base, Calif., at 8:12 EDT this morning.

“We have had a fantastic mission,” Collins said shortly after the crew disembarked from the Shuttle. “We brought Discovery back in great shape. This is a wonderful moment for us all to experience.”

Discovery’s mission, the first of two Return to Flight test missions following the 2003 Columbia accident, was one of the most complex space flights in NASA history. The crew flawlessly executed its to-do list.

After an on-time lift-off from KSC on July 26, the crew tested new capabilities and techniques developed over the past two-and-one-half years to inspect and possibly repair the Space Shuttle in orbit. Collins guided Discovery through an unprecedented back flip maneuver as it approached the International Space Station. The maneuver allowed the Station crew to snap high-resolution photos that added to the wealth of new data mission managers used to ensure Discovery was in good shape to come home.

“It’s going to be hard to top this mission,” NASA Administrator Michael Griffin said. “Everywhere you look, there’s nothing but outstanding success.”

Robinson and Noguchi, with the help of crewmates, completed three spacewalks. The astronauts repaired one Space Station Control Moment Gyroscope and replaced another. Their efforts put all four of the Station’s gyros back into service. They also tested new repair techniques for the Space Shuttle’s heat-shielding outer skin and installed equipment outside the Station.

When two thermal protection tile gap-fillers were spotted jutting out of Discovery’s underside, astronauts and other experts on the ground pulled together to devise a plan to prevent the protrusions from “tripping the boundary layer,” causing higher temperatures on the Shuttle during atmospheric re-entry. Ground controllers sent up plans to the Shuttle-Station complex for Robinson to ride the Station robotic arm beneath the Shuttle and, with surgical precision, pluck out the gap-fillers. Work on the Shuttle underbelly had never been tried before, but with Thomas coordinating, Lawrence and Kelly operating the robotic arms, and fellow spacewalker Noguchi keeping watch, Robinson delicately completed the extraction.

Discovery’s astronauts and the Station crew, Russian Sergei Krikalev and American John Phillips, transferred more than 12,000 pounds of equipment and supplies to the Station. Discovery returned about 7,000 pounds of Station material back to Earth.

The crew got phone calls from two world leaders. President George W. Bush and Japanese Prime Minister Junichiro Koizumi offered congratulations and appreciation for all the astronauts’ hard work.

Commander Collins and the crew also paid tribute to the fallen astronauts of Columbia, as well as others who gave their lives for space exploration.

Over the next several weeks, engineers will process data from STS-114, the first of two test missions for the Space Shuttle. Teams are already at work looking into why a large piece of foam fell off the External Tank during ascent. NASA managers have committed to understanding why the foam came off the tank, and remedying it if necessary, before clearing the next Space Shuttle Return to Flight test mission, STS-121, for flight.

The Discovery astronauts will spend the next few days undergoing medical checkouts, reuniting with their families, and returning to Houston. In about a week, after undergoing preparations at Edwards, Discovery will be ferried back to NASA’s Kennedy Space Center, Fla., atop a modified Boeing-747 aircraft.

For more about the Return to Flight mission, visit:
http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Posted on by Fraser Cain

What Does the Milky Way Look Like?

Spiral galaxy NGC 4565. Image credit: ESO Click to enlarge
How does the Galaxy in which we live look like?

It is almost certain that we will never be able to send a probe out of our Milky Way to take a snapshot, in the same way as the first satellites could do to give us striking images of planet Earth. But astronomers do not need this to imagine what our bigger home resembles. And they have a pretty good idea of it.

The Milky Way with its several hundreds of billion stars is thought to be a relatively flat disc -100,000 light-year across- with a central bulge lying in the direction of the constellation Sagittarius (The Archer) and six spiral arms. The Milky Way has most probably also a central bar made of young, bright stars.

If we can’t take pictures of the Milky Way, we may photograph others galaxies which astronomers think look similar to it. The two galaxies presented here are just two magnificient examples of barred spiral galaxies. One – Messier 83 – is seen face-on, and the other – NGC 4565 – appears edge-on. Together, they give us a nice idea of how the Milky Way may appear from outer space.

These images are based on data obtained with the twin FORS1 and FORS2 (FOcal Reducer and Spectrograph) instruments attached to two ESO’s 8.2-m Unit Telescopes of the Very Large Telescope Array located on Cerro Paranal. The data were extracted from the ESO Science Archive Facility, which contains approximately 50 Terabytes of scientific data and is, since April 1, 2005, open to the worldwide community. These invaluable data have already led to the publication of more than 1000 scientific papers. They also contains many nice examples of beautiful astronomical objects which could be the theme of as many midsummer’s dreams.

NGC 4565

The first galaxy pictured here is NGC 4565, which for obvious reasons is also called the Needle Galaxy. First spotted in 1785 by Uranus’ discoverer, Sir William Herschel (1738-1822), this is one of the most famous example of an edge-on spiral galaxy and is located some 30 million light-years away in the constellation Coma Berenices (Berenice’s Hair). It displays a bright yellowish central bulge that juts out above most impressive dust lanes.

Because it is relatively close (it is only 12 times farther away than Messier 31, the Andromeda galaxy, which is the major galaxy closest to us) and relatively large (roughly one third larger than the Milky Way), it does not fit entirely into the field of view of the FORS instrument (about 7 x 7 arcmin2).

Many background galaxies are also visible in this FORS image, giving full meaning to their nickname of “island universes”.

Messier 83

If our Milky Way were to resemble this one, we certainly would be proud of our home! The beautiful spiral galaxy Messier 83 is located in the southern constellation Hydra (the Water Snake) and is also known as NGC 5236 and as the Southern Pinwheel galaxy. Its distance is about 15 million light-years. Being about twice as small as the Milky Way, its size on the sky is 11×10 arcmin2.

The image show clumpy, well-defined spiral arms that are rich in young stars, while the disc reveals a complex system of intricate dust lanes. This galaxy is known to be a site of vigorous star formation.

Original Source: ESO News Release

Posted on by Fraser Cain

Mars Reconnaissance Orbiter Ready for Thursday Launch

The Mars Reconnaissance Orbiter. Image credit: NASA Click to enlarge
NASA’s Mars Reconnaissance Orbiter is ready for a morning launch on Thursday, Aug. 11. The spacecraft will arrive at Mars in March 2006 for a mission to understand the planet’s water riddles and to advance the exploration of the mysterious red planet.

The mission’s first launch opportunity window is 4:50 to 6:35 a.m. PDT, Thursday. If the launch is postponed, additional launch windows open daily at different times each morning through August. For trips from Earth to Mars, the planets move into good position for only a short period every 26 months. The best launch position is when Earth is about to overtake Mars in their concentric racing lanes around the Sun.

“The teams preparing this orbiter and its launch vehicle have done excellent work and kept to schedule. We have a big spacecraft loaded with advanced instruments for inspecting Mars in greater detail than any previous orbiter, and we have the first Atlas V launch vehicle to carry an interplanetary mission. A very potent and exciting combination,” said NASA’s Mars Exploration Program Director Doug McCuistion.

The mission will lift off from Launch Complex 41, Cape Canaveral Air Force Station, Fla. It is the first government launch of Lockheed Martin’s Atlas V launch vehicle. “We’re ready to fly, counting down through final procedures,” said Chuck Dovale, director for expendable-launch-vehicle launches at NASA Kennedy Space Center, Fla.

When the Mars Reconnaissance Orbiter arrives in March, it begins a half-year “aerobraking” process. The spacecraft will gradually adjust the shape of its orbit by using friction from carefully calculated dips into the top of the Martian atmosphere. The mission?s primary science phase starts in November 2006.

“Mars Reconnaissance Orbiter will give us several times more data about Mars than all previous missions combined,” said James Graf, project manager for the mission at NASA’s Jet Propulsion Laboratory, Pasadena Calif.

Researchers will use the data to study the history and distribution of Martian water. Learning more about what has happened to the water will focus searches for possible past or present Martian life. Observations by the orbiter will also support future Mars missions by examining potential landing sites and providing a communications relay between the Martian surface and Earth.

The craft can transmit about 10 times as much data per minute as any previous Mars spacecraft. This will serve both to convey detailed observations of the Martian surface, subsurface and atmosphere by the instruments on the orbiter and enable data relay from other landers on the Martian surface to Earth. NASA plans to launch the Phoenix Mars Scout in 2007 to land on the far northern Martian surface. NASA is also developing an advanced rover, the Mars Science Laboratory, for launch in 2009.

The mission is managed by JPL, a division of the California Institute of Technology, Pasadena, Calif., for the NASA Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft and is the prime contractor for the project.

NASA’s Launch Services Program at the Kennedy Space Center is responsible for government engineering oversight of the Atlas V, spacecraft/launch vehicle integration and launch day countdown management.

For more information about the Mars Reconnaissance Orbiter on the Web, visit: http://www.nasa.gov/mro.

Original Source: NASA News Release

Posted on by Fraser Cain

Tiny Epimetheus Outside the Rings

Saturn’s moon Epimetheus just beneath the ring. Image credit: NASA/JPL/SSI Click to enlarge.
Saturn’s moon Epimetheus is seen here from just beneath the ring plane, along with Saturn’s intriguing F ring. The bright, knotted core of the F ring is flanked on both sides by thin, dusty strands. The outer part of the A ring is visible at the left. Epimetheus is 116 kilometers (72 miles) across.

Part of the little moon’s night side is illuminated by reflected light from the planet. For a closer view of Epimetheus see Epimetheus: Up-Close and Colorful.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 30, 2005, at a distance of approximately 1.8 million kilometers (1.1 million miles) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 93 degrees. Resolution in the original image was 11 kilometers (7 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Delays for the Earth’s Oxygen Atmosphere

Looking down on Earth. Image credit: NASA Click to enlarge
A number of hypotheses have been used to explain how free oxygen first accumulated in Earth’s atmosphere some 2.4 billion years ago, but a full understanding has proven elusive. Now a new model offers plausible scenarios for how oxygen came to dominate the atmosphere, and why it took at least 300 million years after bacterial photosynthesis started producing oxygen in large quantities.

The big reason for the long delay was that processes such as volcanic gas production acted as sinks to consume free oxygen before it reached levels high enough to take over the atmosphere, said Mark Claire, a University of Washington doctoral student in astronomy and astrobiology. Free oxygen would combine with gases in a volcanic plume to form new compounds, and that process proved to be a significant oxygen sink, he said.

Another sink was iron delivered to the Earth’s outer crust by bombardment from space. Free oxygen was consumed as it oxidized, or rusted, the metal.

But Claire said that just changing the model to reflect different iron content in the outer crust makes a huge difference in when the model shows free oxygen filling the atmosphere. Increasing the actual iron content fivefold would have delayed oxygenation by more than 1 billion years, while cutting iron to one-fifth the actual level would have allowed oxygenation to happen more than 1 billion years earlier.

“We were fairly surprised that we could push the transition a billion years in either direction, because those levels of iron in the outer crust are certainly plausible given the chaotic nature of how Earth formed,” he said.

Claire and colleagues David Catling, a UW affiliate professor in atmospheric sciences, and Kevin Zahnle of the National Aeronautics and Space Administration’s Ames Research Center in California will discuss their model tomorrow (Aug. 9) in Calgary, Alberta, during the Geological Society of America’s Earth System Processes 2 meeting.

Earth’s oxygen supply originated with cyanobacteria, tiny water-dwelling organisms that survive by photosynthesis. In that process, the bacteria convert carbon dioxide and water into organic carbon and free oxygen. But Claire noted that on the early Earth, free oxygen would quickly combine with an abundant element, hydrogen or carbon for instance, to form other compounds, and so free oxygen did not build up in the atmosphere very readily. Methane, a combination of carbon and hydrogen, became a dominant atmospheric gas.

With a sun much fainter and cooler than today, methane buildup warmed the planet to the point that life could survive. But methane was so abundant that it filled the upper reaches of the atmosphere, where such compounds are very rare today. There, ultraviolet exposure caused the methane to decompose and its freed hydrogen escaped into space, Claire said.

The loss of hydrogen atoms to space allowed increasingly greater amounts of free oxygen to oxidize the crust. Over time, that slowly diminished the amount of hydrogen released from the crust by the combination of pressure and temperature that formed the rocks in the crust.

“About 2.4 billion years ago, the long-term geologic sources of oxygen outweighed the sinks in a somewhat permanent fashion,” Claire said. “Escaping to space is the only permanent escape that we envision for the hydrogen, and that drove the planet to a higher oxygen level.”

The model developed by Claire, Catling and Zahnle indicates that as hydrogen atoms stripped from methane escaped into space, greenhouse conditions caused by the methane blanket quickly collapsed. Earth’s average temperature likely cooled by about 30 degrees Celsius, or 54 degrees Fahrenheit, and oxygen was able to dominate the atmosphere because there was no longer an overabundance of hydrogen to consume the oxygen.

The work is funded by NASA’s Astrobiology Institute and the National Science Foundation’s Integrative Graduate Education and Research Traineeship program, both of which foster research to understand life in the universe by examining the limits of life on Earth.

“There is interest in this work not just to know how an oxygen atmosphere came about on Earth but to look for oxygen signatures for other Earth-like planets,” Claire said.

Original Source: UW News Release

Posted on by Fraser Cain

Heavy Bombardments Make the Best Homes… for Microbes

Hills of impact melt breccias. Image credit: Gordon Osinski/CSA Click to enlarge
Meteor impacts are generally regarded as monstrous killers and one of the causes of mass extinctions throughout the history of life. But there is a chance the heavy bombardment of Earth by meteors during the planet’s youth actually spurred early life on our planet, say Canadian geologists.

A study of the Haughton Impact Crater on Devon Island, in the Canadian Arctic, has revealed some very life-friendly features at ground zero. These include hydrothermal systems, blasted rocks that are easier for microbes to inhabit, plus the cozy, protected basin created by the crater itself. If true, impact craters could represent some of the best sites to look for signs of past or present life on Mars and other planets.

A presentation on the biological effects of impacts is scheduled for Monday, 8 August, at Earth System Processes 2, a meeting co-convened by the Geological Society of America and Geological Association of Canada this week in Calgary, Alberta, Canada.

The idea that meteor impacts could benefit or even create conditions suitable for the beginning of early life struck Canadian Space Agency geologist Gordon Osinski while he and colleagues were conducting a geological survey of the 24-kilometer (15-mile) diameter Haughton Crater. Along the rim of the crater they noticed what looked like fossilized hydrothermal pipes, a few meters in diameter.

“That set the bells ringing about possible biological implications,” said Osinski. Hydrothermal systems are thought by many people to be the favourable places for life to evolve.”

Detailed mineralogical analyses have since revealed that when the Haughton meteor smacked into the icy ground 23 million years ago it created not only a crater, but fractured the ground in such a way as to create a system of steamy hydrothermal springs reaching temperatures of 250 degrees C. The heat appears to have gradually dropped over a period of tens of thousands of years, the researchers report.

Besides providing heat and cracking the ground, the impact also created pore spaces in otherwise dense granitic rocks, giving microbes more access to the minerals and the surfaces inside the rocks ? basically more real estate and more supplies.

The shocked rocks are also more translucent, which would be beneficial to organisms that possessing with any photosynthetic capabilities.

A crater shape itself also might serve as a protective environment, says Osinski. As such, impact craters are also good places to store evidence of past life. On Earth many craters fill with water and become lakes. Lakes accumulate sediments, the layers of which are a geological archive of the time after the crater formed. The Haughton Impact crater, for instance, contains the only Miocene-age sediments in the entire Canadian Arctic.

“One of the most interesting aspects of the Haughton Impact Crater is that it’s in a polar desert,” said Osinski. The dry, frigid weather makes for a barren landscape that’s easy to study, he said. The same features make it one of the more Mars-like places on Earth.

“Most people put impacts with mass extinctions,” said Osinski. “What we’re trying to say is that following the impact, the impact sites are actually more favorable to life than the surrounding terrain.”

It’s interesting to note, says Osinski, that on Earth the heaviest meteor bombardment of the planet happened at about the same time as life is believed to have started: around 3.8 billion years ago. Impact craters of that age were long ago erased on Earth by erosion, volcanic resurfacing and plate tectonics.

But other planets and moons – including Mars – still bear the cosmic scars of that early debris-clogged period in the solar system. It may be possible, therefore, that the best places to look for at least fossil evidence of life on Mars is inside those very same craters, he said.

“What we’re doing is trying to narrow down the search area,” said Osinski.

Original Source: GSA News Release