Abstract
Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years. This is testified by the widespread occurrence of mid-latitude gullies: small catchment-fan systems. However, there are no direct estimates of the amount and frequency of liquid water generation during these periods. Here we determine debris-flow size, frequency and associated water volumes in Istok crater, and show that debris flows occurred at Earth-like frequencies during high-obliquity periods in the last million years on Mars. Results further imply that local accumulations of snow/ice within gullies were much more voluminous than currently predicted; melting must have yielded centimetres of liquid water in catchments; and recent aqueous activity in some mid-latitude craters was much more frequent than previously anticipated.
Highlights
Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years
These analyses show that local accumulations of snow/ice within gullies were in the order of centimetres to decimetres during periods of high obliquity in the last Myr
The pole-facing slope of Istok crater hosts a bajada, a series of coalescing fans, with abundant debris-flow deposits[10], which are among the best preserved found on Mars to date
Summary
Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years. We address these questions by quantifying debris-flow size, frequency and associated liquid water content on Mars, in the very young Istok crater in Aonia Terra (Fig. 1) (formed 0.1–1 Myr ago; best-fit age: B0.19 Ma; 45.11° S; 274.2° E)[10]. These analyses show that local accumulations of snow/ice within gullies were in the order of centimetres to decimetres during periods of high obliquity in the last Myr. These analyses show that local accumulations of snow/ice within gullies were in the order of centimetres to decimetres during periods of high obliquity in the last Myr Melting of this snow/ice must have yielded centimetres of liquid water in the gully catchments to produce the observed debris-flow volumes. Debris flows were much more frequent than previously anticipated and occurred at Earth-like frequencies in Istok crater at high obliquity
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