When NASA new horizons In 2015, the mission flew by Pluto, giving humans the first glimpse of the isolated world’s vast depressions. It was named Sputnik Planitia. Sputnik Planitia, which is about the size of Mexico and dominates one of Pluto’s hemispheres, is likely the result of an impact — but few impact craters have Sputnik Planitia’s distinctive pear-shaped shape.
How Sputnik Planitia formed remains unknown, but researchers have now painted a possible picture of its origins. They say it’s possible that a Swiss-sized object hit Pluto at a shallow angle long ago. If true, the image would also hint at what Pluto’s interior might look like beneath its cold surface.
related: Why isn’t Pluto a planet?
“Most people think Sputnik Planitia was created by an impact, but no one has been able to explain its unique pear-shaped shape,” Harry Ballantyne, an astronomer at the University of Bern in Switzerland, told Space.com.
Sputnik Planitia’s shape and massive size—approximately 2,000 kilometers long (1,243 miles long) and 1,600 kilometers wide (994 miles wide)—are not the only reasons planetary scientists observe it with curiosity. Whatever created the formation managed to carve the dent 4 kilometers (2.5 miles) deep; the bottom of the crack appears to be a sheet of frozen nitrogen ice. Gravity should have slowly rotated Pluto so that the dent and its missing mass ended up at one of Pluto’s poles, but strangely, Sputnik Planitia remained around the equator.
a popular theory suggestion Sputnik Planitia is actually a hint of the global ocean buried beneath Pluto’s surface. After a giant impact, liquid water from the ocean might have risen to fill the gap, which would then have been covered with a layer of nitrogen, explaining why Sputnik Planitia remains at the equator. Still, some scientists remain unconvinced.
“I have never bought into the idea that a global ocean would be needed for a satellite to finally reach the equator,” Eric Asphaugan astronomer at the University of Arizona told Space.com. “It seems to me that if you start and end with an entity that can withstand that kind of impact, it’s much easier to explain it.”
So Asphaug, Ballantyne and their colleagues began running three-dimensional simulations to understand what conditions might have led to the formation of Sputnik Planitia. The strange shape of this feature suggests that the dent’s maker struck Pluto obliquely, rather than head-on. This allowed them to simulate a 700-kilometer-wide (435-mile-wide) object – a ball of ice and rock – impacting a Pluto-like world. The object was also designed to present a rocky core within a shell of water ice and deliver impact at a shallow angle of 30 degrees. In fact, not only did this situation lead to the formation of the pear-shaped crater, but the team’s simulations showed that the impactor’s core remained buried beneath Sputnik Planitia, giving it the extra mass needed to stay on the equator.
The authors say future research is still needed to expand these concepts, both to understand how Sputnik Planitia evolved over billions of years and to understand how collisions occurred in this far corner of the solar system.
“There’s still a lot to learn about planetary collisions,” Adne DentonA planetary scientist at the University of Arizona and another author of the paper told Space.com. “Especially for the Kuiper Belt, there’s a lot of uncertainty about what happens when icy and rocky bodies collide.”
Pluto’s interior may help us finally understand these dynamics, but for clearer answers, we may have to wait for another mission. While New Horizons’ visit to Pluto was an impressive feat, the probe didn’t do anything other than simply fly by Pluto, meaning the mission really just scratched the surface of the former planet. Future missions may be able to orbit Pluto and probe its interior, including by measuring the world’s gravity field.
“We need geophysical data collected around the Moon and Mars that allow us to determine the interior structure of these objects in such detail,” Denton told Space.com. “There is a lot of information about the interior of Pluto, and orbiting Pluto. is the best way.”
Researchers publish their findings in journal natural astronomy April 15th.
#Plutos #heartshaped #scar #hold #clues #frozen #worlds #history
Image Source : www.space.com