Aspera (Energetic Neutral Atoms Analyser)will measure ions, electrons and energetic neutral atoms in
the outer atmosphere to reveal the numbers of oxygen and
hydrogen atoms (the constituents of water) interacting with
the solar wind and the regions of such interaction. Constant
bombardment by the stream of charged particles pouring
out from the Sun is thought to be responsible for the loss of
Mars’ atmosphere. The planet no longer has a global
magnetic field to deflect the solar wind, which is
consequently free to interact unhindered with atoms of
atmospheric gas and sweep them out into space. "We will
be able to see this plasma escaping the planet and so estimate
how much atmosphere has been lost over billions of years,"
says Rickard Lundin, ASPERA PI from the Swedish Institute of
Space Physics in Kiruna, Sweden.