Tag: Greenland

A Clue Into The Makeup of Jupiter’s Moon Europa Provided by the Greenland Ice Sheet

Double ridge ice formations seen on Europa are similar to formations detected on the Greenland Ice Sheet. This artist’s rendering shows how double ridges on the surface of Jupiter’s moon Europa may form over shallow, refreezing water pockets within the ice shell. This mechanism is based on the study of an analogous double ridge feature found on Earth’s Greenland Ice Sheet. (Justice Blaine Wainwright)

Europa’s ice crust is crossed by thousands of double ridges, pairs of long parallel raised lines with a small valleys in between, sometimes as much as hundreds of miles long and skyscraper-height tall rims. While these double ridges are ubiquitous on Europa’s surface, how they form remains something of a mystery to scientists.

Dustin Schroeder, an associate professor of geophysics at Stanford University’s School of Earth, Energy & Environmental Sciences, was working on an issue related to climate change when he saw double ridges similar to those seen on Europa here on Earth.  The ridges, in Northwest Greenland, were tiny when compared with those on Europa, but the found the same “M”-shaped crest as found everywhere on that Jovian moon.

“We were working on something totally different related to climate change and its impact on the surface of Greenland when we saw these tiny double ridges – and we were able to see the ridges go from ‘not formed’ to ‘formed,’ ” Schroeder said.

Could the double ridges be forming as a result of processes similar to those that form the double ridges on Europa?

If so, then Greenland would provide a possibly important new window into a central question about Europa:  Is that thick ice shell surrounding the subsurface ocean completely solid, or does it have what are called “water sills” within the shell?

This is important because, as the Nature Communications paper concludes, “If the same process is responsible for Europa’s double ridges, our results suggest that shallow liquid water is spatially and temporally ubiquitous across Europa’s ice shell.”

Or as Schroeder put it, “If the mechanism we see in Greenland is how these things happen on Europa, it suggests there’s water everywhere,” he said in a release.

They can make this inference because the double ridges formed in Greenland are the known, and detectable, result of the dynamics of subsurface water surrounded by the ice sheet.

Surface imagery comparison of a double ridge on Europa (a) and on Earth (b), on the Northwest Greenland Ice Sheet.

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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

A Unique Science Expedition to Greenland

Greenland from above, where the ice sheet is melting to form lakes and to expose rocks not visible for millennia. @Susan Oliver

It is my very good fortune to report that I have just arrived in Greenland for quite a scientific adventure.
 
Over the next days, a group of scientists (along with me and NASA videographer Mike Toillion) will be traveling to the site of the stromatolite that might, or might not, be the oldest remains of life on Earth.  In a 2016 Nature paper, it was described as having been fossilized about 3.7 billion years ago.
 
Another Nature paper two years later challenged the biological origins of the “fossil,” and the debate has been pretty vigorous since.

Vigorously debated putative stromatolite from the Isua Peninsula, Greenland.

We’ll be helicoptering about 100 miles northeast of the capital Nuuk to get to the Isua peninsula, where the oldest (or almost the oldest, depending on who you choose to follow) rock formations on Earth can be found. Three days and two nights on the ice, or what we hope is still ice. And then a day or more of scientific debate.

I will be writing about this and more (some folks involved the Mars 2020 mission will also be testing instruments at the site) for Many Worlds in the days and weeks ahead.

To me this is an important story not only because of the possible age of the stromatolite find.  If confirmed, it would move back the presence of identified life on Earth by 200 million years.

It is also important because of the fact that scientists with different views on this important issue have traveled thousands of miles to go to the site together and try to reach a consensus—or at least to vigorously argue their cases.  Doesn’t often happen in such high profile science.

Greenstone Belt formations on the Isua Peninsula where our team will be headed.

 
Greenland has, of course, been in the news of late for reasons ranging  worrisome purchase offers to far more worrisome warming.  Remarkable are the “moulin” — which drain the water running on the ice sheet and send it down thousands of feet to the water or land below. 
Kind of a ice black hole.

A “moulin” in Greenland that acts as a very deep drain for water melting on the ice sheet.

Now it’s in my news because, well, I’m here in Greenland, to learn, to report back, and to take in everything this spectacular place has to offer.
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