A shower of
shooting stars has been recorded by instruments on Mars for the first time,
astronomers say.
Meteors
have been spotted
before by the Mars rovers, but no device has ever detected a full shower
until now.
United
Kingdom astronomers
predicted the event by tracking a comet's path near Mars, then comparing their
forecast with Mars Global Surveyor (MGS) satellite data of the red planet's ionosphere
— the upper reaches of atmosphere teeming with charged particles.
"Just
as we can predict meteor outbursts at Earth, such as the
Leonids [shower that occurs every November], we can also predict when
meteor showers are going to occur at Mars and Venus," said Apostolos
Christou, an astronomer at the U.K.'s Armagh
Observatory who helped predict the martian meteoric event.
Christou is
set to present findings about the meteor-showering pass of comet 79P/du
Toit-Hartley at the Royal Astronomical Society's National Astronomy Meeting in Belfast on April 2.
Meteor
central
Just as on
Earth, meteor showers on Mars can occur when a planet passes through the dusty
trail of a comet.
There are
no conventional photos of the meteors in the new findings, but studying the
brightness and length of meteor streaks in optical and radio data, Christou said,
can help determine the age, size and composition of a comet's
core.
Scientists
think four times as many comets dust Mars with their tails compared to our home
planet, as a high proportion of comets hang out near Jupiter — the red planet's
next-closest neighbor. So there could be many more meteor showers visible from
Mars than from Earth.
Some even
blame such frequent comet dusting of Mars for the puzzling course
change of Mariner 4, the first spacecraft to visit Mars, in the 1960s.
Fuzzy
details
Christou said
detecting the distant meteor shower wasn't easy.
"We
believe that shooting stars should appear at Venus and Mars with a similar
brightness to those we see at Earth," he said. "However, as we are
not in a position to watch them in the martian sky directly, we have to sift
through satellite data to look for evidence of particles burning up in the
upper atmosphere."
Christou
and his colleagues predicted six meteor showers caused by the intersection of
Mars with dust trails from comet 79P/du Toit-Hartley since 1997, which was when
the
MGS satellite entered orbit.
The team
pinpointed meteor streaks indirectly by measuring disturbances in electrical density
of Mars' atmosphere with the spacecraft's radio communication system.
Out of the two
showers MGS could have recorded — in 2003 or 2005 — Christou and his colleagues
found hints of a shower only in data of the 2003 event.
"We
don't see anything in the 2005 data because the meteors burned up deeper in the
atmosphere," he said, adding that the depth would cover up an electrical
signature. "If we are going to get a clear picture of what is going on, we
need more optical and ionospheric observations of meteor showers at both the
Earth and Mars so we can establish a definitive link between cause and effect."
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