What Happened to Mars? A Planetary Mystery   
       
   Nov. 12, 2013:  Billions of years ago when the planets of our solar system   
   were still young, Mars was a very different world.  Liquid water flowed in   
   long rivers that emptied into lakes and shallow seas. A thick atmosphere   
   blanketed the planet and kept it warm. In this cozy environment, living   
   microbes might have found a home, 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.   
       
   Today, Mars is bitter cold and desiccated. The planet's thin, wispy atmosphere   
   provides scant cover for a surface marked by dry riverbeds and empty lakes. If   
   Martian microbes still exist, they're probably eking out a meager existence   
   somewhere beneath the dusty Martian soil.   
       
   What happened? This haunting question has long puzzled scientists. To find the   
   answer, NASA is sending a new orbiter to Mars called MAVEN (Mars Atmosphere   
   and Volatile Evolution).   
       
   A new ScienceCast video ponders the question, What Happened to Mars? Play it   
       
   http://www.youtube.com/watch?v=etL2ZhqGNCs   
       
   "The goal of MAVEN is to figure out what processes were responsible for those   
   changes in Martian climate," says Bruce Jakosky, Principal Investigator for   
   MAVEN at the University of Colorado at Boulder.   
       
   Scheduled for launch in Nov. 2013, and due to arrive in Sept. 2014, MAVEN is   
   bristling with instruments to study Mars' upper atmosphere.  That's where many   
   researchers believe the answer lies.   
       
   Auroras Underfoot (signup)The only way Mars could have been wet and warm 4   
   billion years ago, is if it also had a thick atmosphere.  CO2 in the Martian   
   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.   
       
   Something caused Mars to lose that blanket.  One possibility is the solar   
   wind.  Unlike Earth, Mars is not protected by a global magnetic field.   
   Instead, it has "magnetic umbrellas" scattered around the planet that shelter   
   only part of the atmosphere. Erosion of exposed areas by solar wind might have   
   slowly stripped the atmosphere away over billions of years. Recent   
   measurements of isotopes in the Martian atmosphere by Mars rover Curiosity   
   support this idea: light isotopes of hydrogen and argon are depleted compared   
   to their heavier counterparts, suggesting that they have floated away into   
   space.   
       
   http://tinyurl.com/ldp9xck   
       
   NASA's MAVEN spacecraft is hoisted to the top of a Atlas V rocket at Cape   
   Canaveral.  Launch is scheduled for Nov. 18th. MoreScientists have also   
   speculated that the planet's surface might have absorbed the CO2 and locked it   
   up in minerals such as carbonate. However, this theory has faded in recent   
   years as Mars rovers and orbiters have failed to find enough carbonate to   
   account for the missing gas.   
       
   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. 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 during   
   the last four billion years. "MAVEN will determine if loss to space was the   
   most important player in driving Martian climate change," Jakosky says.   
       
   In the grand scheme of the Solar System, Earth orbits alongside a world that   
   began with as much promise for life as our own . yet turned out so   
   differently. After all these years, MAVEN could write the final chapter in a   
   haunting planetary mystery.   
       
   Credits:   
       
    Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More information:   
       
   Mars Atmosphere and Volatile Evolution -- MAVEN home page   
       
   MAVEN social media: Facebook and Twitter   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.96   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)