Tag: Mars 2020 rover

On The Rugged Frontier Of The Hunt For Signs Of Life On Early Earth And Ancient Mars

The vigorously debated finding from the Isua greenstone or supercrustal belt, a 1,200-square-mile area of ancient rocks in Greenland.  Proponents say the rises, from .4 to 1.6 inches tall, are  biosignatures of bacteria and sediment mounds that made up stromatolites almost 3.8 billion years ago.  Critics say additional testing has shown they are the result of non-biological forces.  (Nature and Nutman et al.)

Seldom does one rock outcrop get so many visitors in a day, especially when that outcrop is located in rugged, frigid terrain abutting the Greenland Ice Sheet and can be reached only by helicopter.

But this has been a specimen of great importance and notoriety since it appeared from beneath the snow pack some eight years ago. That’s when it was first identified by two startled geologists as something very different from what they had seen in four decades of scouring the geologically revelatory region – the gnarled Isua supercrustal belt – for fossil signs of very early life.

Since that discovery the rock outcrop has been featured in a top journal and later throughout the world as potentially containing the earliest signature of life on Earth – the outlines of half inch to almost two inch-high stromatolite structures between 3.7 and 3.8 billion years old.

The Isua greenstone, or supracrustal belt contains some of the oldest known rocks and outcrops in the world, and is about 100 miles northeast of the capital, Nuuk.

If Earth could support the life needed to form primitive but hardly uncomplicated stromatolites that close to the initial cooling of the planet, then the emergence of life might not be so excruciatingly complex after all. Maybe if the conditions are at all conducive for life on a planet (early Mars comes quickly to mind) then life will probably appear.

Extraordinary claims in science, however, require extraordinary proof, and inevitably other scientists will want to test the claims.

Within two years of that initial ancient stromatolite splash in a Nature paper (led by veteran geologist Allen Nutman of the University of Wollongong in Australia), the same journal published a study that disputed many of the key observations and conclusions of the once-hailed ancient stromatolite discovery.  The paper concluded the outcrop had no signs of early life at all.

Debates and disputes are common in geology as the samples get older,  and especially in high profile science with important implications.  In this case, the implications of what is in the rocks reach into the solar system and the cosmos. … Read more

Where Should We Look for Ancient Biosignatures on Mars in 2020?

Jerezo crater contains a delta with abundant sedimentary layers that are the kind most likely to preserve fossil life, and so is one of three landing sites in the running for the Mars 2020 mission. The image has been colored to better show features of the site. (NASA)

One of the great successes of the Curiosity mission to Mars is that the rover landed at what turned out to be a goldmine of a location.

The mission has once and for all determined that the planet was habitable at least during its early days, that it contains the organic building blocks of life, and that liquid water ran and formed lakes.  And this leaves out the more basic Mars science that some day will some day produce new headline results.

The process of anointing a successor destination for NASA’s 2020 rover mission to Mars has been going on for several years now, and the field was narrowed to three possibilities earlier this year.

Because some of the primary goals of the 2020 mission differ from those of the Curiosity mission, the potential landing sites are unlike Gale Crater and all share certain features that are, not surprising, promising in terms of the new goals.  What’s new is the requirement that the 2020 mission will search for biosignatures of life in the ancient rocks and to identify, pick up and store rocks samples for later return to Earth.

Given those (and other) science goals, the leaders of the Mars 2020 mission — and the large community of scientists eager to become a formal or informal part of the mission — have been looking for sites where water was clearly present in the distant past and where conditions seem best for actually preserving fossil microbial biosignatures that may have been present.

This is quite a dramatic change, and will be the first NASA mission sent to look for life — albeit fossilized and ancient life — since the Viking missions of four decades ago.

“What we’re down to now is three sites featuring different kinds of ancient water settings,” said Kenneth Williford of NASA’s Jet Propulsion Lab.  He’s deputy project scientist for the 2020 mission and a specialist in identifying fossil remnants of lifeforms in ancient Earth rocks.

“On the list we have a site that was clearly a river delta, one that had a large concentration of subsurface water, and another that may be the site of a possible hot spring. … Read more

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