Solar storms 'could sandblast the moon'
Washington: Solar storms and associated
(CMEs) could significantly erode the
lunar surface, according to a new set of computer simulations
by NASA scientists.
In addition to removing a surprisingly large amount of
material from the lunar surface, this could be a major method
of atmospheric loss for planets like Mars that are unprotected
by a global magnetic field, say the planetary scientists led
by Rosemary Killen at NASA's Goddard Space Flight Center.
CMEs are basically an intense gust of the normal solar
wind, a diffuse stream of electrically conductive gas called
plasma that's blown outward from the surface of the Sun into
The moon has just the barest wisp of an atmosphere,
technically called an exosphere because it is so tenuous,
which leaves it vulnerable to CME effects. The plasma from
CMEs impacts the lunar surface, and atoms from the surface are
ejected in a process called "sputtering."
"We found that when this massive cloud of plasma strikes
the moon, it acts like a sandblaster and easily removes
volatile material from the surface.
"The model predicts 100 to 200 tons of lunar material --
the equivalent of 10 dump truck loads -- could be stripped off
the lunar surface during the typical 2-day passage of a CME,"
said William Farrell, a team member.
This is the first time researchers have attempted to
predict the effects of a CME on the moon. "Connecting various
models together to mimic conditions during solar storms is a
major goal of the DREAM project," said Farrell.
Plasma is created when energetic events, like intense
heat or radiation, remove electrons from the atoms in a gas,
turning the atoms into electrically charged particles -- ions.
The Sun is so hot that the gas is emitted in the form of
free ions and electrons called the solar wind plasma. Ejection
of atoms from a surface or an atmosphere by plasma ions is
"Sputtering is among the top five processes that create
the moon's exosphere under normal solar conditions, but our
model predicts that during a CME, it becomes the dominant
method by far, with up to 50 times the yield of the other
methods," said Killen.
The findings have been published in the 'Journal of
Geophysical Research Planets'.