A team at the Natural History Museum (NHM), London is paving the way for
future rovers to search for meteorites on Mars. The scientists are using the
NHM’s extensive meteorite collection to test the spectral instruments
destined for the ExoMars rover Rosalind Franklin, and develop tools to
identify meteorites on the surface of the red planet. The project is being
presented on 23 July at the virtual National Astronomy Meeting 2021.
The cratered surface of our nearest planetary neighbour has a long and
complex history, and searching for rocks amidst more rocks may seem like a
futile activity. Despite this, Martian rovers statistically have a
significantly higher ‘find per mile’ success rate than dedicated meteorite
hunts on Earth: for every kilometre travelled by a Mars rover, approximately
one meteorite is found, even though the rovers have not been specifically
looking for them up till now.
However, as part of the European Space Agency's upcoming ExoMars mission,
the next rover - named Rosalind Franklin, after the chemist best known for
her pioneering work on DNA - will drill down into the Martian surface to
sample the soil, analyse its composition and search for evidence of past or
present life buried underground.
Meteorites are important pieces of evidence that can help us understand this
story; once a meteorite lands on a planet, it is subjected to the same
atmospheric conditions as the rest of the surface. Chemical and physical
weathering can provide information on climate weathering rates and
water-rock interactions, meteorite sizes and distribution can help to infer
information about the density of the atmosphere, and stony meteorites could
be a potential delivery mechanism for organic materials to Mars.
“Meteorites act as a witness plate across geological time,” said Sara
Motaghian, the PhD student at the NHM and Imperial College London who is
carrying out the work. “Generally, the surfaces of Mars we are exploring are
incredibly ancient, meaning there have been billions of years for the
surface to accumulate these meteorites and lock in information from across
Mars’ past.”
The team are looking in particular at the use of multispectral imaging with
the PanCam instrument, hoping to be able to highlight features in images
that could be associated with meteorites as the rover moves across the
surface. They are also investigating the possibility of using pattern
recognition techniques to distinguish features such as Widmanstätten
patterns, which can be revealed by extreme weathering.
The launch of the ExoMars rover was originally scheduled for 2020, however
was delayed until 2022 due to technical issues and growing concerns over the
coronavirus pandemic. Once the rover reaches Mars in 2023, the team hope
that their work will allow meteorites on the surface to be studied for
longer by the Rosalind Franklin rover before it drives on, helping to build
a more complete understanding of the Martian surface and its history, if
any, of life.
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