[meteorite-list] Meteor Showers Observed in the Martian Atmosphere

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 4 Apr 2008 17:12:19 -0700 (PDT)
Message-ID: <200804050012.RAA29096_at_zagami.jpl.nasa.gov>

http://www.astronomynow.com/news/080403marsmeteors/

Meteor showers observed in the Martian atmosphere
BY EMILY BALDWIN
ASTRONOMY NOW
April 3, 2008

A storm of shooting stars has, for the first time, been detected in the
Martian atmosphere by a team of scientists based at the Armagh Observatory.

The data was taken from the Mars Global Surveyor (MGS) satellite, which
has been orbiting Mars since 1997, and is derived from the tell-tale
signatures that meteor showers leave imprinted in the Martian
atmosphere. "When meteors burn up in the atmosphere the metals contained
within them are ionised by sunlight to form a layer of plasma," explains
Dr Apostolos Christou, who presented the results at the National
Astronomy Meeting on Wednesday. "This happens at an altitude of about
80-95 kilometres for Mars, and although the metallic ions cannot be
observed directly by the MGS instruments, evidence for the plasma layer
is inferred by monitoring the electron density in the atmosphere."

Christou and his colleagues have developed a model to predict meteor
showers caused by the intersection of Mars with dust trails from comet
79P/du Toit-Hartley. From the model, the team identified six predicted
meteor showers, for which data was analysed for two showers in April
2003 and March 2005.

For the 2003 dataset the team found that the ionospheric disturbances
appeared at the exact time of the meteor shower and in the predicted
location. "It's difficult for the observations to be correlated to
anything else," says Christou. "The ionisation patterns live for a few
hours corresponding to the time of the meteor shower. It was also at the
right altitude and it happened on the hemisphere of Mars that was facing
the shower at the time."

The 2005 dataset, however, yielded no features indicative of a meteor
shower. "We speculate that the meteors in this case were larger than the
2003 outburst, maybe 5 millimetres in diameter compared to 1 millimetre,
and so they burnt up deeper in the Martian atmosphere where their
ionisation effects were less efficient, so the signatures could not be
observed."

What is evident is that more data is required to understand exactly how
the ionosphere reacts to meteor influx. The team hope to test their
predictions further when comet 79P intersects Mars' orbit again in 2010,
2014, 2016 and 2024. There are also plans to investigate the possibility
of making observations with Europe's ExoMars mission, which is due to
land on Mars in 2015.
Received on Fri 04 Apr 2008 08:12:19 PM PDT