Tag: taphonomy

The Hows and Whys of Mars Sample Return

Combining two images, this mosaic shows a close-up view of the rock target named “Yeehgo” taken by the SuperCam instrument on NASA’s Perseverance rover on Mars. To be compatible with the rover’s software, “Yeehgo” is an alternative spelling of “Yéigo,” the Navajo word for diligent.
(NASA/JPL-Caltech/LANL/CNES/CNRS/ASU/MSSS)

One of the fondest dreams and top priorities of space science for years has been  to bring a piece of Mars back to Earth to study in the kind of depth possible only in a cutting-edge laboratory.

While the instruments on Mars rovers can tell us a lot,  returning a sample to study here on Earth is seen as the  way to ultimately tease out the deepest secrets of the composition of Mars, its geological and geochemical history and possibly the presence of life, life fossils or of the precursor molecules  of life.

But bringing such a sample to Earth is extraordinarily difficult.  Unlike solar system bodies that have been sampled back on Earth — the moon, a comet and some asteroids — Mars has the remains of an atmosphere.  That means any samples would have to lift off in a rocket brought to Mars and with some significant propulsive power, a task that so far has been a technical bridge too far.

That is changing now and the Mars Sample Return mission has begun.  The landing of the Perseverance rover in Jezero Crater on Mars signaled that commencement and the rover will be used to identify, drill into and collect intriguing bits of Mars.  This is a long-term project, with the best case scenario seeing those Mars samples arriving on Earth in a decade.  So this entirely unprecedented, high-stakes campaign will be playing out for a long time.

“I think that Mars scientists would like to return as much sample as possible,” said Lindsay Hays, NASA Mars Sample Return deputy program scientist.  “Being able to return samples that we collected with purpose is how we take the next step in our exploration of Mars.”

“And it seems that there are still so many unknowns, even in our solar system, even with the planets right next door, that every time we do something new, we answer a couple of questions that we hoped to and but also find a whole bunch of new things that we never expected.”

“I am so excited to see what comes of this adventure.  And I think that is a feeling shared by Mars scientists and planetary scientists broadly.”… Read more

The Ancient Mars Water Story, Updated

Rendering of Gale Lake some 3.5 billion years ago, when Mars was warmer and much wetter. The Curiosity mission is finding that Gale Crater water-changed rock is everywhere.

Rendering of Gale Lake some 3.5 billion years ago, when Mars was warmer and much wetter. The Curiosity mission is finding that rocke in Gale Crater changed by water everywhere. (Evan Williams, with data from the Mars Reconnaissance Orbiter HIRISE project)

Before the Curiosity rover landed on Mars, NASA’s “follow the water”maxim had already delivered results that suggested a watery past and just maybe some water not far below the surface today that would periodically break through on sun-facing slopes.

While tantalizing — after all, the potential presence of liquid water on a exoplanet’s surface is central to concluding that it is, or once was, habitable — it was far from complete and never confirmed via essential ground-truthing.

Curiosity famously provided that confirmation early on with the discovery of pebbles that had clearly been shaped in the presence of flowing surface water, followed by the months in Yellowknife Bay which proved geologically, geochemically and morphologically the long-ago presence of substantial amounts of early Martian water.

Some of the earliest drilling was into mudstone that looked very much like a dried up basin or marsh, and that was exactly what Curiosity scientists determined it was, at a minimum.  It took many months for Curiosity leaders to ever use the word “lake” to describe what had once existed on the site, but now it is a consensus description.

Since the presence of a fossil lake was confirmed and announced, the water story has taken something of a backseat as the rover made its challenging and revelatory way across the lowlands of Gale Crater, through some dune fields and onto the Murray formation — a large geological unit that is connected to the base of Mount Sharp itself.  And all along the path of the rover’s traverse mudstone and sandstone were present, a clear indication of ever larger amounts of water.

I spoke recently with geologist and biogeologist John Grotzinger, the former NASA chief scientist for Curiosity and now a member of the science team, to get a sense of how things had progressed for the Gale water story.  He said there was no longer any doubt that the crater was once quite filled with water.

“We have  not seen a single rock at Gale that doesn’t say that the planet was wet.  In the areas where the rover has driven, I’d be very comfortable now in saying that the surface and ground water was often present for millions to tens of millions of years.”… Read more

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