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Last Updated: 1:05 PM GMT on November 07, 2009
— Last Comment: 3:39 PM GMT on November 07, 2009
From NASA
A Tale of Planetary Woe 11.06.2009 Nov. 6, 2009: Once upon a time — roughly four billion years ago — Mars was warm and wet, much like Earth. Liquid water flowed on the Martian surface in long rivers that emptied into shallow seas. A thick atmosphere blanketed the planet and kept it warm. Living microbes might have even arisen, some scientists believe, starting Mars down the path toward becoming a second life-filled planet next door to our own. But that's not how things turned out. Mars today is bitter cold and bone dry. The rivers and seas are long gone. Its atmosphere is thin and wispy, and if Martian microbes still exist, they're probably eking out a meager existence somewhere beneath the dusty Martian soil. What happened? Why did Mars dry up and freeze over? These haunting questions have long puzzled scientists. A few years from now we might finally know the answer, thanks to a new orbiter NASA will send to Mars called MAVEN (short for Mars Atmosphere and Volatile Evolution). "The goal of MAVEN is to figure out what processes were responsible for those changes in the climate," says Bruce Jakosky, Principal Investigator for MAVEN at the University of Colorado at Boulder. One way or another, scientists believe, Mars must have lost its most precious asset: its thick atmosphere of carbon dioxide. CO2 in Mars's atmosphere is a greenhouse gas, just as it is in our own atmosphere. A thick blanket of CO2 and other greenhouse gases would have provided the warmer temperatures and greater atmospheric pressure required to keep liquid water from freezing solid or boiling away. Over the last four billion years, Mars somehow lost most of that blanket. Scientists have proposed various theories for how that loss happened. Perhaps an asteroid impact blew most of the atmosphere into space in one catastrophic event. Or maybe erosion by the solar wind — a stream of charged particles emanating from the sun — could have slowly stripped the atmosphere away over eons. The planet's surface might also have absorbed the CO2 and locked it up in minerals such as carbonate. Ultimately, nobody knows for sure where all the missing CO2 went. MAVEN will be the first mission to Mars specifically designed to help scientists understand the ongoing escape of CO2 and other gases into space. The probe will orbit Mars for at least one Earth-year. At the elliptical orbit's low point, MAVEN will be 125 km above the surface; its high point will take it more than 6000 km out into space. This wide range of altitudes will enable MAVEN to sample Mars's atmosphere more thoroughly than ever before. As it orbits, MAVEN's instruments will track ions and molecules in this broad cross-section of the Martian atmosphere, thoroughly documenting the flow of CO2 and other molecules into space for the first time. Once Jakosky and his colleagues know how quickly Mars is losing CO2 right now, they can extrapolate backward in time to estimate the total amount lost to space during the last four billion years. "MAVEN will determine if [loss to space] was the most important player," Jakosky says. But just as important as "how much?" is the question of "how?" Conventional wisdom holds that Mars's atmosphere is vulnerable because the planet lacks a global magnetic field. Earth's magnetic field stretches far out into space and envelopes the whole planet in a protective bubble that deflects the solar wind. Mars has only regional, patchy magnetic fields that cover relatively small areas of the planet, mostly in the southern hemisphere. The rest of the atmosphere is fully exposed to the solar wind. So the loss could be caused by the slow erosion of the atmosphere in these exposed areas. David Brain of UC Berkeley has proposed another, seemingly contrary possibility. These small magnetic fields might actually hasten the loss of Mars's atmosphere, Brain suggests. The solar wind might buffet those magnetic field lines, occasionally pinching off a "bubble" of field lines that then drifts off into space — carrying a large chunk of the atmosphere with it. If so, having a partial magnetic field might be worse than having none at all. This possibility was described in a 2008 Science@NASA story, "Solar Wind Rips Up Martian Atmosphere." Some evidence from NASA's Mars Global Surveyor spacecraft supports Brain's theory, but decisive measurements will have to wait for MAVEN, currently scheduled to launch in 2013. The mission will be a big step toward understanding what happened to Mars — how it ended up so cold and dry after such a warm and watery beginning. After all these years, MAVEN could write the final chapter in a haunting tale of planetary woe.
(Who knew?) From NASA Hidden Territory on Mercury Revealed 11.03.2009Nov. 3, 2009: The MESSENGER spacecraft's third flyby of the planet Mercury has given scientists, for the first time, an almost complete view of the planet's surface and revealed some dramatic changes in Mercury's comet-like tail."The new images remind us that Mercury continues to hold surprises," says Sean Solomon, principal investigator for the mission and director of the Department of Terrestria...
INDONESIAN ASTEROID: Earlier this month, with no warning, a ~10-meter wide asteroid hit Earth's atmosphere above Indonesia and exploded. The break-up was so powerful, it triggered nuclear test ban sensors thousands of kilometers away. A just-released analysis of infrasound data shows that the asteroid detonated with an energy equivalent of about 50 kton of TNT, similar to a small atomic bomb. This significant impact has received relatively little attention in Wes...
[ I know it's sure been hiding out around HERE lately....] From NASA The Sun's Sneaky Variability 10.27.2009October 27, 2009: Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. Clouds of gas big enough to swallow planets break away from the sun and billow into space. It's a flamboyant display of stellar power....
From Space Weather [dot] comBIG SUNSPOT: The sun is showing signs of life. Sunspot 1029 emerged over the weekend, and it is crackling with B- and C-class solar flares. The active region's magnetic polarity identifies it as a member of new Solar Cycle 24. If its growth continues apace, sunspot 1029 could soon become the biggest sunspot of 2009. Check http://spaceweather.com for animations and updates.MONDAY NIGHT SKY SHOW: When the sun sets on Monday, Oct. 26th, go...
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