Early discoveries by NASA's newest Mars orbiter are starting to reveal key features about the loss of the planet's atmosphere to space over time.The Mars Atmosphere and Volatile Evolution (MAVEN) mission is observing the upper atmosphere of Mars to help understand climate change on the planet.The observations reveal a new process by which the solar wind can penetrate deep into a planetary atmosphere.They include the first comprehensive measurements of the composition of Mars' upper atmosphere and electrically charged ionosphere.
The results also offer an unprecedented view of ions as they gain the energy that will lead to their to escape from the atmosphere."We are beginning to see the links in a chain that begins with solar-driven processes acting on gas in the upper atmosphere and leads to atmospheric loss," said Bruce Jakosky, MAVEN principal investigator with the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder.
"Over the course of the full mission, we will be able to fill in this picture and really understand the processes by which the atmosphere changed over time," said Jakosky.
On each orbit around Mars, MAVEN dips into ionosphere - the layer of ions and electrons extending from about 75 to 300 miles above the surface.This layer serves as a kind of shield around the planet, deflecting the solar wind, an intense stream of hot, high-energy particles from the sun.Scientists have thought for a long time that measurements of the solar wind could be made only before these particles hit the invisible boundary of the ionosphere.MAVEN's Solar Wind Ion Analyzer, however, has discovered a stream of solar-wind particles that are not deflected but penetrate deep into Mars' upper atmosphere and ionosphere.
New insight into how gases leave the atmosphere is being provided by the spacecraft's Suprathermal and Thermal Ion Composition (STATIC) instrument.Within hours after being turned on at Mars, STATIC detected the "polar plume" of ions escaping from Mars. This measurement is important in determining the rate of atmospheric loss.The findings are among the first returns from MAVEN mission that entered its science phase Nov 16.