On our planet, we’re quite
in luck if we see a few hundred meteors an hour during a meteor shower. But if
you were on Mars about three years ago, nevertheless, you would have witnessed
something extraordinary – 108,000 meteors per hour, the biggest meteor shower
ever in recorded history on any planet.
This meteor shower was a
result of Comet C/2013 A1 (Siding Spring) zipping past the planet on October
19, 2014. We were lucky to have a spacecraft in circling the planet back then,
and what they observed was unbelievable.
Observations from the event were offered
few days ago at the European Planetary Science Congress (EPSC) 2017 in Riga,
Latvia.
Dr Beatriz Sanchez-Cano from
the University of Leicester, who co-presented the findings, said “This is one
of the most exciting planetary events that we’ll see in our lifetime. Mars was
literally engulfed by the coma, the comet’s outer atmosphere, for several
hours.”
Siding Spring flew past Mars
at a distance of 140,000 kilometers (87,000 miles), an occasion that’s believed
to occur only once every 100,000 years. And as it did so, it left a track of
debris that hit the Martian atmosphere.
Observations by NASA’s MAVEN
Orbiter show that there would have been 30 meteors per second in the Martian
sky for up to three hours – or 108,000 meteors per hour. That is truly an
incredible amount. On Earth, our record shower was probably the Leonids meteor
shower in 1833, which saw 100,000 meteors per hour dazzle observers.
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| Hubble's view of Comet Siding Spring. NASA/ESA/J.-Y. Li (Planetary Science Institute) |
Studying the event was
somewhat difficult because it appears Mars was hit by an eruption from the Sun
about 44 hours before the comet flew past. But MAVEN gathered enough data to
reveal the biggest ever meteor shower in the Solar System.
Meteor showers on Earth are
caused when we fly through the debris trail of a comet. These happen on regular
occasions, such as the Perseids every August from Comet Swift-Tuttle, or the
Leonids every November from Comet Tempel-Tuttle.
For Mars, this really was a
once-in-a-lifetime event. Siding Spring originated in the Oort cloud, a vast
region of comets on the edge of the Solar System, and is now heading back in
that direction. It will be millions of years before it comes past again. Maybe
next time, we’ll be ready and waiting on the surface of Mars.