Pluto may be giant comet made up of comets, study says

Maps assembled using data from the Ralph instrument indicate regions rich in methane, nitrogen, carbon monoxide and water ices. Scientists combined these data with Rosetta’s comet 67P data to develop a proposed "giant comet" model for Pluto formation. Photo by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

May 29 (UPI) — After studying data from two interplanetary probes, researchers think Pluto may have formed from a mass of a billion comets, according to a new study.

Scientists at the Southwest Research Institute investigated two theories about the formation of what was previously known as the farthest-out planet in the solar system — the comet theory, and a solar theory that the dwarf planet formed from very cold ices similar to those of the Sun — using data from NASA’s New Horizons probe and the European Space Agency’s Rosetta probe.

The researchers integrated data from two of the probe’s missions, one to Pluto and one to a comet called 67P, focusing on the amount of nitrogen and carbon dioxide now present at the dwarf planet, leaving them with the two theories.

“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,” Dr. Christopher Glein, a researcher at SwRI’s Space Science and Engineering Division, said in a press release. “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.”

To determine the amount of nitrogen present on Pluto now, and lost over time, the researchers worked to calculate how much carbon monoxide is there as well, and how much has been lost over time.

For the study, published recently in the journal Icarus, the researchers focused on the glacier Sputnik Planitia, which is located in the left lobe of the Tombaugh Regio, a heart-shaped region of Pluto’s surface.

Based on the nitrogen on the dwarf planet, and low level of carbon monoxide detected there, researchers say carbon monoxide on Pluto is either trapped in ice on its surface or it was destroyed by exposure to liquid water.

“We’ve developed what we call ‘the giant comet’ cosmochemical model of Pluto formation,” Glein said. “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 chemical composition to 67P, the comet explored by Rosetta.”

Glein said the new research suggests the initial chemical makeup of Pluto was modified by water, but that overall more work will be needed to solidify a theory.


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