Billions of years ago, Mars shifted from rivers and lakes to dry dunes; NASA says Curiosity’s hematite crystals may help date that climate shift in rock

Mars hasn’t all the time been the dusty, dry planet that we see in footage immediately. NASA’s Curiosity rover has been climbing Mount Sharp in Gale Crater for greater than a decade, passing by means of historical lake beds, dried-up streams and fields of historical sand dunes. For a very long time, scientists have identified that Mars transitioned from a heat, moist planet to a chilly, dry one. What they didn’t have was a dependable option to date when this occurred precisely. In a brand new research printed within the journal Science, researchers Marek Szczerba and Tanya Peretyazhko could lastly have discovered that timeline in a standard rust-colored mineral referred to as hematite.

A rusty clue buried within the rock

Hematite is a type of iron oxide, primarily rust, and iron reacting with water produces it: proof that scientists have lengthy used to substantiate water as soon as existed someplace on Mars. What’s new on this research is extra particular: the tiny crystals that make up hematite develop to completely different sizes relying on how heat the water was and the way lengthy it lasted. Which means hematite is extra than simply proof of water flowing as soon as on Mars. It might additionally present a clue about how lengthy that water hung round. The workforce studied 20 rock samples Curiosity drilled from completely different depths inside Gale Crater, NASA stories. Because the deeper layers of rock shaped earlier within the historical past of Mars, scientists can journey up the crater wall to get a rock file that spans an extended interval of the planet’s early local weather.

How Curiosity reads the rocks like tree rings

The Curiosity rover carries an instrument referred to as CheMin, brief for Chemistry and Mineralogy. It fires X-rays at powdered rock samples and measures how the rays scatter, a way referred to as X-ray diffraction. This implies scientists can measure the exact measurement of mineral crystals, one thing orbiting satellites can’t do from house. Thomas Bristow, the instrument’s principal investigator at NASA’s Ames Analysis Heart, mentioned the information reveals the scale and form of hematite crystals, in addition to close by minerals that solely ground-level rover devices can seize.

Deeper rocks stayed moist for thousands and thousands of years longer
The research discovered that hematite crystals in larger, youthful layers of rock remained beneath 10 nanometers. Crystals from the older, decrease layers grew a lot bigger, some reaching 65 nanometers. The workforce additionally famous that the mineral goethite, which is mostly related to hematite, was current within the higher layers however not within the decrease layers. That progress did not occur when the rock first shaped; it occurred afterward, as heat groundwater stored transferring by means of these already-buried layers for thousands and thousands of years, giving the crystals time to develop by means of a course of referred to as Ostwald ripening, the place small crystals dissolve and feed the expansion of bigger ones. On this hotter, much less acidic setting, goethite additionally slowly modifications to hematite. Altogether, the findings counsel heat groundwater could have continued for as much as 4.7 million years in Gale Crater’s deepest, oldest rock layers even because the floor of Mars was already cooling, in line with the research.”What we discovered was that heat and moist situations had been current for prolonged intervals in buried rocks, regardless of Mars’ local weather changing into colder,” mentioned Peretyazhko, in feedback to NASA Science.

Why the underground story issues greater than the floor one

This aligns with what Curiosity has already seen on the floor. The rover’s climb up Mount Sharp has taken it from historical lake-bed clays into rock layers shaped by dry, windblown dunes, NASA’s Jet Propulsion Laboratory says. Ashwin Vasavada, who’s the undertaking scientist for the Curiosity mission, explains this phenomenon succinctly when he says that deposits from lakes finally transitioned to these from dunes, typically with stream movement.

The hematite research provides a deeper layer of proof: water could have stored transferring underground for thousands and thousands of years after the floor lakes had already dried up and vanished. This issues to anybody fascinated about whether or not Mars as soon as supported life, as a result of water deep underground, protected against chilly and radiation, is commonly thought of a extra promising place to search for liveable situations than the floor.

What this implies for the hunt for all times on Mars

None of this proves life existed on Mars. It provides scientists a brand new, bodily option to hint how lengthy water continued in numerous layers of Mars’ historical rock, utilizing samples the rover has already collected, reasonably than relying solely on pc fashions. It additionally feeds the concept Mars didn’t dry out in a single day. The change was gradual, pockets of heat and moisture lingering underground lengthy after the floor had gone chilly and naked.