Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p61c0356b&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #P61C-0356
Physics
5407 Atmospheres: Evolution, 5421 Interactions With Particles And Fields, 5440 Magnetic Fields And Magnetism, 6225 Mars
Scientific paper
The magnetic environment near Mars plays a critical role in the escape of atmosphere to space. It is therefore possible that crustal magnetic sources have an effect on atmospheric escape rates, both presently and in the past. Using simple models of the Martian magnetic morphology (constrained by data from MGS MAG) we will explore the quantitative effect that the presence of crustal sources might have on the three main loss processes believed to be important at Mars in the present epoch: photochemical escape, ion pickup from the solar wind, and sputtering. Crustal sources should affect loss via the two latter processes in two different ways - by shielding regions of Mars' atmosphere locally from solar wind-related ionization processes and by trapping photoions on closed magnetic field lines associated with the crust. Additionally, reconnection of closed magnetic field lines to the passing solar wind magnetic field should allow direct access of the solar wind to lower regions of Mars' atmosphere. The presence and strength of crustal sources at Mars has major implications for atmospheric loss rates over Martian history. First, we now know that a Martian dynamo once existed. An active dynamo would have prevented the access of the solar wind to the Martian atmosphere. Additionally, if crustal sources were much stronger in the past and occurred over a large fraction of the Martian subsurface then these sources would have acted as an effective global magnetosphere, preventing access of the solar wind to the Martian atmosphere. We will discuss the current constraints on atmospheric loss rates over Martian history indicated by crustal sources, and suggest future observations that might address this important question.
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