The similarity between many Martian valleys and the
subglacial channels on Devon Island in the Canadian Arctic motivated the
authors to conduct their comparative study. “Devon Island is one of the best
analogues we have for Mars here on Earth — it is a cold, dry, polar desert, and
the glaciation is largely cold-based,” says co-author Gordon Osinski, professor
in Western University’s department of earth sciences and Institute for Earth
and Space Exploration.
In total, the researchers analyzed more than 10,000
Martian valleys, using a novel algorithm to infer their underlying erosion
processes. “These results are the first evidence for extensive subglacial
erosion driven by channelized meltwater drainage beneath an ancient ice sheet
on Mars,” says co-author Mark Jellinek, professor in UBC’s department of earth,
ocean and atmospheric sciences. “The findings demonstrate that only a fraction
of valley networks match patterns typical of surface water erosion, which is in
marked contrast to the conventional view. Using the geomorphology of Mars’
surface to rigorously reconstruct the character and evolution of the planet in
a statistically meaningful way is, frankly, revolutionary.”
Grau Galofre’s theory also helps explain how the
valleys would have formed 3.8 billion years ago on a planet that is further
away from the sun than Earth, during a time when the sun was less intense.
“Climate modelling predicts that Mars’ ancient climate was much cooler during
the time of valley network formation,” says Grau Galofre, currently a SESE
Exploration Post-doctoral Fellow at Arizona State University. “We tried to put
everything together and bring up a hypothesis that hadn’t really been
considered: that channels and valleys networks can form under ice sheets, as
part of the drainage system that forms naturally under an ice sheet when
there’s water accumulated at the base.”
These environments would also support better survival
conditions for possible ancient life on Mars. A sheet of ice would lend more
protection and stability of underlying water, as well as providing shelter from
solar radiation in the absence of a magnetic field — something Mars once had,
but which disappeared billions of years ago.
While Grau Galofre’s research was focused on Mars, the
analytical tools she developed for this work can be applied to uncover more
about the early history of our own planet. Jellinek says he intends to use
these new algorithms to analyze and explore erosion features left over from
very early Earth history.
“Currently we can reconstruct rigorously the history
of global glaciation on Earth going back about a million to five million
years,” says Jellinek. “Anna’s work will enable us to explore the advance and
retreat of ice sheets back to at least 35 million years ago — to the beginnings
of Antarctica, or earlier — back in time well before the age of our oldest ice
cores. These are very elegant analytical tools.”
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