Sorry if anyone came here in the past couple of days expecting/hoping to find a post all about the amazing news of Curiosity’s discovery of an ancient riverbed at Gale Crater, but I’ve been AFK (to use a quaint old early-web term! Look it up, kids!) doing, you know, real-life stuff… but yes, fascinating news from Mars: the images taken by Curiosity have revealed that she is effectively driving across the remains of an ancient martian riverbed – the rounded, smooth stones seen by her cameras were made that way by the eroding action of water running over and around them, possibly billions of years ago, water which flowed into the crater and across its floor after entering through a gap in the crater wall. It’s not entirely unexpected news – one of the reasons Curiosity was sent to Gale in the first place was because orbital images showed signs of “aluvial fans” spread out across the crater floor, fans of debris left behind after water had poured into and across the crater from outside – but it’s always brilliant to have a theory confirmed by “ground truth”, so congratulations to all the science team!
Here’s the official press release, reproduced here to 1) save me time, and 2) prevent me from explaining something badly or incorrectly…!
RELEASE : 12-338
Scientists are studying the images of stones cemented into a layer of conglomerate rock. The sizes and shapes of stones offer clues to the speed and distance of a long-ago stream’s flow.
“From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep,” said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. “Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it.”
The finding site lies between the north rim of Gale Crater and the base of Mount Sharp, a mountain inside the crater. Earlier imaging of the region from Mars orbit allows for additional interpretation of the gravel-bearing conglomerate. The imagery shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds.
The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.
The discovery comes from examining two outcrops, called “Hottah” and “Link” with the telephoto capability of Curiosity’s mast camera during the first 40 days after landing. Those observations followed up on earlier hints from another outcrop, which was exposed by thruster exhaust as Curiosity, the Mars Science Laboratory Project’s rover, touched down.
“Hottah looks like someone jack-hammered up a slab of city sidewalk, but it’s really a tilted block of an ancient streambed,” said Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena.
The gravels in conglomerates at both outcrops range in size from a grain of sand to a golf ball. Some are angular, but many are rounded.
“The shapes tell you they were transported and the sizes tell you they couldn’t be transported by wind. They were transported by water flow,” said Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute in Tucson, Ariz.
The science team may use Curiosity to learn the elemental composition of the material, which holds the conglomerate together, revealing more characteristics of the wet environment that formed these deposits. The stones in the conglomerate provide a sampling from above the crater rim, so the team may also examine several of them to learn about broader regional geology.
The slope of Mount Sharp in Gale Crater remains the rover’s main destination. Clay and sulfate minerals detected there from orbit can be good preservers of carbon-based organic chemicals that are potential ingredients for life.
“A long-flowing stream can be a habitable environment,” said Grotzinger. “It is not our top choice as an environment for preservation of organics, though. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment.”
During the two-year prime mission of the Mars Science Laboratory, researchers will use Curiosity’s 10 instruments to investigate whether areas in Gale Crater have ever offered environmental conditions favorable for microbial life.
What’s Curiosity up to now? Well, looking at the latest images to come back she’s within spitting distance of “Glenelg, her first hard science target…
You want to see that in 3D? Of course you do…
…and when Curiosity looks at the ground, she sees *this*…
Beautiful in 3D too…
There are mysteries and magicv waiting to be found here, don’t you think?
Meanwhile, other images sent back by Curiosity might, possibly, maybe, perhaps suggest that she’s preparing to scoop up some loose material for the first time, to test that side of her science package works… I LOVE this next picture, with the contrast between the muted, almost pastel hues of the dusty, gritty, rocky ground and the cold, stark metal of the scoop…
But obviously the Big News is the discovery that water once flowed – if not rushed – across this part of Mars, and I’ll come back to that as and when time allows. I’m working on a new astropoem about it right now, which I hope some of you will like.