Scientists introduce cosmochemical model for Pluto formation

May 23, 2018, Southwest Research Institute
NASA's New Horizons spacecraft captured this image of Sputnik Planitia — a glacial expanse rich in nitrogen, carbon monoxide and methane ices — that forms the left lobe of a heart-shaped feature on Pluto’s surface. SwRI scientists studied the dwarf planet’s nitrogen and carbon monoxide composition to develop a new theory for its formation. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Southwest Research Institute scientists integrated NASA's New Horizons discoveries with data from ESA's Rosetta mission to develop a new theory about how Pluto may have formed at the edge of our solar system.

"We've developed what we call 'the giant comet' cosmochemical model of Pluto formation," said Dr. Christopher Glein of SwRI's Space Science and Engineering Division. The research is described in a paper published online today in Icarus. At the heart of the research is the nitrogen-rich ice in Sputnik Planitia, a large glacier that forms the left lobe of the bright Tombaugh Regio feature on Pluto's surface. "We found an intriguing consistency between the estimated amount of nitrogen inside the glacier and the amount that would be expected if Pluto was formed by the agglomeration of roughly a billion comets or other Kuiper Belt objects similar in to 67P, the comet explored by Rosetta."

In addition to the comet model, scientists also investigated a solar model, with Pluto forming from very cold ices that would have had a chemical composition that more closely matches that of the Sun.

Scientists needed to understand not only the nitrogen present at Pluto now—in its atmosphere and in glaciers—but also how much of the volatile element potentially could have leaked out of the atmosphere and into space over the eons. They then needed to reconcile the proportion of to nitrogen to get a more complete picture. Ultimately, the low abundance of carbon monoxide at Pluto points to burial in surface ices or to destruction from .

New Horizons not only showed humanity what Pluto looks like, but also provided information on the composition of Pluto’s atmosphere and surface. These maps — assembled using data from the Ralph instrument — indicate regions rich in methane (CH4), nitrogen (N2), carbon monoxide (CO) and water (H2O) ices. Sputnik Planitia shows an especially strong signature of nitrogen near the equator. SwRI scientists combined these data with Rosetta’s comet 67P data to develop a proposed “giant comet” model for Pluto formation. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
"Our research suggests that Pluto's initial chemical makeup, inherited from cometary building blocks, was chemically modified by liquid water, perhaps even in a subsurface ocean," Glein said. However, the solar model also satisfies some constraints. While the research pointed to some interesting possibilities, many questions remain to be answered.

"This research builds upon the fantastic successes of the New Horizons and Rosetta missions to expand our understanding of the origin and evolution of Pluto," said Glein. "Using chemistry as a detective's tool, we are able to trace certain features we see on Pluto today to formation processes from long ago. This leads to a new appreciation of the richness of Pluto's 'life story,' which we are only starting to grasp."

The paper, "Primordial N2 provides a cosmochemical explanation for the existence of Sputnik Planitia, Pluto," is coauthored by Glein and Dr. J. Hunter Waite Jr., an SwRI program director.

Explore further: Shedding light on Pluto's glaciers

More information: "Primordial N2 Provides a Cosmochemical Explanation for the Existence of Sputnik Planitia, Pluto," Christopher Glein & J. Hunter Waite Jr., 2018 May 23, Icarus. DOI: 10.1016/j.icarus.2018.05.007 , dx.doi.org/10.1016/j.icarus.2018.05.007 , arxiv.org/abs/1805.09285

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Uncle Ira
5 / 5 (1) May 28, 2018
If the Pluto gets another demotion it will make a lot of peoples around here mad.
eric96
not rated yet May 28, 2018
"about how Pluto may have formed at the edge of our solar system."

It is erroneous to think that pluto is or is close to the edge of our solar system. The technical edge of the solar system is "that which the sun cannot bring into orbit". AU is the distance between the sun and earth. Pluto is 40 AU. According to simulations, at its furthest point Planet 9 is 1200 AU while still being in a simulated orbit. Do you see how ridiculous calling pluto the edge of the solar system is? Also pluto is not even a planet. Therefore, the grammatically and astronomically correct sentence would be ""about how Pluto formed away from prime planetary formation. Unless someone discovers planet 9, Neptune is the last planet or orbital body that demonstrates gravitational dominance. Mercury cheats by being close to the sun and having a small orbit.
granville583762
5 / 5 (3) Jun 01, 2018
A planet has become a farce, or is that a research paper
EROS isn't a planet, neither is PLUTO and now MERCURY isn't a planet, with these research papers emerging apace, there isn't going to be any planets left at this rate
Mike Brown: best known as the man who killed Pluto removing 2 planets from our solar system where as Clyde William Tombaugh received the credit for discovering our ninth planet PLUTO
Mike Brown receives no credit for finding our identically sized 10th planet ERIS! By killing the definition of a planet he has prevented himself receiving due credit for finding our 10th planet EROS.
This is like rewriting Kepler's planetary orbital laws every time EROS and PLUTO go flying past, correction "Lump of ICE" because once you have a definition you have to stick with it!
They don't even qualify for dwarf status, one day there will be serious comments on an article concerning orbiting lumps of ice and it will be concerning PLUTO. We are already discussing it!

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