#astronomy Gale Crater on Mars: An Historical Lake or Simply Puddles? – Sky & Telescope

August 17, 2021 - Comment

For nearly twenty years, NASA has been “following the water” on Mars. That is the rationale Curiosity Rover was despatched to Gale Crater in 2012. On the time of launch, scientists thought the location seemed like an enormous lakebed. However now, an unbiased evaluation of each Curiosity information and up to date imagery taken from


For nearly twenty years, NASA has been “following the water” on Mars. That is the rationale Curiosity Rover was despatched to Gale Crater in 2012. On the time of launch, scientists thought the location seemed like an enormous lakebed.

However now, an unbiased evaluation of each Curiosity information and up to date imagery taken from orbit means that the looks of the rock layers beforehand considered deposits laid down by water really come from wind and chemical weathering as an alternative.

Gale CraterCuriosity’s picture of Mount Sharp in Gale Crater exhibits layered sedimentary rocks. The rover has been driving from the ground of the crater up by way of these hills as a way to perceive how the rocks change from decrease within the part (older) to increased within the part (youthful).
NASA’s Mars Curiosity Rover

The brand new examine by PhD pupil Jiacheng Liu (The College of Hong Kong) and colleagues seems within the August sixth Science Advances. They start by declaring that regardless of early observations that indicated Gale Crater as soon as held a big physique of water, few of the rocks Curiosity has examined really appear to be lake deposits.

The crew thinks that this discrepancy is greatest defined if the crater solely ever had a small smattering of little ponds. Then the vast majority of the bottom explored so far would greatest be defined as basalt sand and silt. The layers of various sorts of rock, which have been thought to have been shaped by water exercise, might as an alternative have been created by wind in a caustic ambiance.

Beforehand, international research of Mars confirmed a mineralogical transition from iron and magnesium clays to aluminium clays to sulphate rocks. There are totally different theories about what this shifting floor composition would possibly imply. Some suppose it is likely to be proof of an amazing environmental transition, maybe the one which noticed Mars change from a hotter and wetter world to the icy desert panorama it’s immediately. Others suppose it is likely to be extra difficult than that.

“Sulphates are like a sort of salt,” says crew member Joe Michalski. “So these youthful minerals would possibly characterize a drying out of the planet. However this does not essentially imply international local weather change occurred at that second.”

On the very starting of its journey, Curiosity recognized some skinny mudstone on the backside of Gale Crater, which probably shaped when mud settled out of calm water. However since then, because the rover has traveled as much as the bottom of Mount Sharp, it has not seen any extra lakeform rocks, but it surely has seen a gradual change within the chemical content material of the samples.

Information from Curiosity appear to point that components, corresponding to aluminum, that keep put beneath chemical weathering situations grow to be extra prevalent at increased altitudes. Different components which are extra simply dispersed, corresponding to iron, grow to be scarcer. This push-and-pull relationship is just like what we see on historical, uncovered rock formations on Earth, which used to have a really totally different ambiance than it does immediately. The researchers argue that the rocks in Gale Crater have been chemically weathered in a low-oxygen greenhouse ambiance containing methane and hydrogen gasoline. 

Two scenarios for water in Gale CraterThese pictures of Gale Crater present elevation colorized in blue. The picture on the left exhibits the usual mannequin, during which Gale Crater as soon as hosted a big lake. The picture on the proper exhibits what Liu and colleagues suggest: Solely small, shallow lakes ever existed on the ground of Gale Crater. Wind deposited a lot of the sediments, which weathered beneath precipitation or ice-melt. A star marks the rover’s touchdown web site.
ESA / HRSC / DLR

The Mars Science Laboratory (NASA’s Curiosity group) have attributed the compositional shift within the Gale crater rocks to the unique “massive lake speculation”. However this new evaluation means that the information is extra ambiguous.

“This new paper says you do not really want a lot water in any respect,” says Bradley Thomson (College of Tennessee-Knoxville), who was not concerned within the examine. “It factors out a doable ambiguity within the information that solely extra information—much more samples and even pattern return—might resolve.”

Perseverance Rover is trying to gather samples for an eventual return to Earth, and it’s doable that these might present extra definitive clues to Mars’s water historical past. Till then, scientists have to be content material with watching Curiosity’s gradual trek up Mount Sharp, information level by single information level, developing a believable idea of the crater’s previous.



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