WASHINGTON: Images taken of Mars from orbit dating back as far as the 1970s have captured curious dark streaks running down the sides of cliffs and crater walls that some scientists have construed as possible evidence of flows of liquid water, suggesting that the planet harbours environments suitable for living organisms.A new study casts doubt on that interpretation. Examining about 500,000 of these sinewy features spotted in satellite images, researchers concluded they were created probably through dry processes that left the superficial appearance of liquid flows, underscoring the view of Mars as a desert planet currently inhospitable to life – at least on its surface. The data indicated that formation of these streaks is driven by the accumulation of fine-grain dust from the Martian atmosphere on sloped terrain that is then knocked down the slopes by triggers such as wind gusts, meteorite impacts and marsquakes.“The tiny dust particles can create flow-like patterns without liquid. This phenomenon occurs because extremely fine dust can behave similarly to a liquid when disturbed,” said Adomas Valantinas, co-leader of the study published on Monday in the journal Nature Communications. “It’s similar to how dry sand can flow like water when poured. But on Mars, the ultra-fine particles and low gravity enhance these fluid-like properties, creating features that might be mistaken for water flows.” The study examined about 87,000 satellite images, including those obtained between 2006 and 2020 of slope streaks, which form suddenly and fade over a period of years.

It remains possible that small amounts of water could mix with enough salt in the ground to create a flow even on Mars. That raises the possibility the slope streaks, if caused by wet conditions, could be habitable niches. “It all comes back to habitability… If slope streaks and recurring slope lineae (shorter-lived features) would really be driven by liquid water or brines, they could create a niche for life. However, if they are not tied to wet processes, this allows us to focus our attention on other, more promising locations,” said study co-leader Valentin Bickel.