Influence of Dust Storm Adsorptive Properties on the Atmospheric Water
Content of Mars
Abstract
Martian global dust storms can raise large amounts of dust into the
atmosphere. This dust has the ability to carry adsorbed water with it
into the atmosphere. Once it arrives in the atmosphere, the dust can
either adsorb additional water or release water vapor. What then happens
when you introduce dust that may be carrying significant amounts of
water with it that can turn to water vapor? We examined this process
numerically by inserting dust into the atmosphere and re-equilibrating
the dust with the vapor. We used the two main analogs for Martian
regolith, volcanic tuff and palagonite. Palagonite could adsorb a
maximum of about 11 wt % and volcanic tuff can adsorb up to 1 wt % of
water. Water that is adsorbed on the dust grain while it is still on the
surface will eventually be carried up and distributed in the atmosphere.
Surface and atmospheric temperatures prior to and during the dust storm
conditions affect two major variables: the amount of water carried up
from the surface dust and the equilibrium between water vapor and
adsorbed water. We found that water raised along with palagonite dust
could increase the total water content of the atmosphere by up to about
20 % during the peak of a high opacity dust storm. Despite this
increase, there was only a 1 % increase in water vapor. Thus, water in
the adsorbed form represents a significant fraction of the water that
can be transported during dust storms. Water introduced to the
atmosphere via this method may be a significant contributor to the
overall atmospheric water cycle.