Tag: abigail allwood

PIXL: A New NASA Instrument For Ferreting Out Clues of Ancient Life on Mars


Extremely high definition images of the com ponents of rocks and mud as taken by PIXL, the Planetary Instrument for X-ray Lithochemistry .   On the Mars 2020 rover, PIXL  will have significantly greater capabilities than previous similar instruments sent to Mars.  Rather than reporting bulk compositions averaged over several square centimeters, it will identify precisely where in the rock each element resides. With spatial resolution of about 300 micrometers, PIXL will conduct the first ever petrology investigations on Mars, correlating elemental compositions with visible rock textures . (NASA)J

The search for life, or signs of past life beyond Earth is now a central issue in space science, is central to the mission of NASA, and is actually a potentially breakthrough discovery in the making  for humanity.    The scientific stakes could hardly be higher.

But identifying evidence of ancient microbial life – and refuting all reasonable non-biological explanations for that evidence — is stunningly difficult.

As recent wrangling over Earth’s oldest rocks in Greenland has shown, determining the provenance of a deep-time biosignature even here on Earth is extraordinarily difficult. In 2016, scientists reported discovery of 3,700 million yr-old stromatolites in the Isua geological area of Greenland.

Just three years later, a field workshop held at the Isua discovery site brought experts from around the world to examine the intriguing structures and see whether the evidence cleared the very high bar needed to accept a biological interpretation. While the scientists who published the initial discovery held their ground, not one of the other scientists felt convinced by the evidence before them.  Watching and listening as the different scientists presented their cases was a tutorial in the innumerable factors involved in coming to any conclusion.

Now think about trying to wrestle with similar or more complex issues on Mars, of how scientists can reach of level of confidence to report that a sign (or hint) of past life has apparently been found.

As it turns out, the woman who led the Greenland expedition — Abigail Allwood of NASA’s Jet Propulsion Lab — is also one of the key players in the upcoming effort to find biosignatures on Mars.  She is the principal investigator of the Planetary Instrument for X-ray Lithochemistry (PIXL) that will sit on the extendable arm of the rover, and it has capabilities to see in detail the composition of Mars samples as never before.

The instrument has, of course, been rigorously tested to understand what it can and cannot do. … Read more

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

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