The Pluto team updates science from the edge of the solar system

Nearly eight years after its historic flyby of Pluto, NASA’s New Horizons probe is preparing for another round of observations from the icy edge of the solar system–and this time, its field of view will range from Uranus and Neptune to the distant cosmic background beyond our galaxy.

Scientists on the New Horizons team shared their latest discoveries, and provided a preview of what’s to come, this week Planetary and Moon Science Conference In The Woodlands, Texas.

It’s been 17 years since New Horizons’ piano-sized spacecraft launched toward Pluto and the Kuiper Belt. The primary mission culminated in 2015 when the probe passed Pluto, but the adventure moved on to a second chapter that focused on a smaller ship. , a bilobed body called Arrokoth – a name derived from the Powhatan/Algonquin word meaning “sky”.

Arrokoth Origins

Alan Stern A Planetary world At the Southwest Research Institute serving as the mission’s principal investigator, he said careful study of Arrokoth’s structure has yielded new insights about the early days of the solar system.

“Because this object orbits so far from the sun, it has always been deep frozen,” Stern explained. “the UV There are much lower than in the inner solar system, as well as collision rates. And so, like its brethren across the Kuiper Belt, Arrokoth is very primitive, undeveloped in this deep freeze over all these billions of years.”

Stern and his colleagues note that Arrokoth appears to have been built from smaller piles of icy material, as if a bunch of snowballs were stuck together to form a larger cluster.

“Individual lobes have similar characteristics … This is evidence of their origin, which we think tells us something very important about the composition of Arrokoth,” Stern said. “And that, precisely, when the cloud of material which had come to make Arrokoth was collapsing…that cloud apparently produced bodies of similar size, those mounds, which came together to form the larger lobe.”

Stern said the new findings about the properties of the ridges are “a very important clue to how these small planets formed across the outer solar system, and possibly even in the inner solar system.” Additional computer modeling could help scientists understand why the hills are so similar to each other, and add new details to their picture of planet formation.

The roving poles of Pluto

Planetary scientists say Pluto’s axis of rotation took a significant tilt early in its history, causing a shift in the latitudes and longitudes of surface features. “Pluto has basically flipped on its side,” said New Horizons co-investigator Oliver White of the SETI Institute. “The locations of the rotational axes moved hundreds if not thousands of miles—if you imagine, like moving San Francisco to New York on Earth. It’s a very significant event. But we still don’t know much about true polar wanderings on Pluto.”

The New Horizons team analyzed the mass distribution on Pluto and determined that the formation of Sputnik Planitia, a sea of ​​frozen nitrogen that forms part of the dwarf planet’s heart-shaped feature, may have played a major role in the polar flip.

White pointed to an ancient system of ridges and troughs that may have been Pluto’s original equator before the true circumnavigation occurred. “We are seeing signs of ancient landscapes that formed in places and in ways that we cannot explain in Pluto’s current orientation,” he said in a press release. “We propose that these are because they were formed when Pluto was oriented differently in its early history, and then were transported to its current location by a true polar wander.”

blades of ice

Ishan Mishra, a science team contributor from NASA’s Jet Propulsion Laboratory, focused on a group of jagged terrain made almost entirely of methane ice, at the edge of New Horizons’ visible hemisphere at the time of closest approach.

“It’s very reminiscent of ‘repentance’ on the ground…in the Atacama Desert in Chile, which is that terrain formed by the sublimation of water-ice deposits,” he said. “On Earth, it’s a few meters high, but on Pluto, it’s hundreds of meters high and it’s formed from methane deposits.”

Mishra and colleagues found that features associated with the bladed terrain imaged in detail by New Horizons during closest approach — for example, methane uptake and surface roughness — were also present in wider regions on Pluto’s “far side.”

“It appears that the blade terrain may be one of the most common terrains on Pluto,” Mishra said.

upcoming attraction

In the coming months and years, the New Horizons science team plans to look back at Uranus and Neptune — and look ahead at the vast expanse beyond our solar system and our Milky Way galaxy. “We have a lot of interesting observations coming soon, starting in August, spanning astrophysics and heliophysics as well as planetary science,” said New Horizons co-investigator Will Grundy of Lowell Observatory in Arizona.

New Horizons will take long-distance images of Uranus and Neptune from an unusual angle. “We’re seeing light scattered in a direction that you can’t see from Earth or the inner solar system,” Grundy said. “We’ll take pictures as the planets rotate, so we can see their evolving cloud structures coming into the illuminated part…and rotating outward as the atmosphere develops.”

The Hubble Space Telescope will observe Uranus and Neptune in parallel with New Horizons’ Pale Blue Dot campaign. “The advantage of this is that what Hubble will see is what the cloud patterns are doing that day, and at the same time that New Horizons is seeing them change as they rotate,” Grundy said.

The science team will scan the distant skies for the potential next flyby target of New Horizons, Stern said, as well as other Kuiper Belt objects in the distance.

The probe will also study the properties of the outer heliosphere. “This is the cocoon of the sun’s influence, before we go out to interstellar medium Where Voyager [probes] “No spacecraft except Voyager and Pioneers have ever been this way. New Horizons carries capabilities that those early spacecraft didn’t have the technology for, or simply didn’t have the necessary hardware for,” Stern said.

Stern noted that New Horizons was overtaken by the faint, hazy glow of sunlight scattered by interplanetary dust — the so-called zodiacal light. “This dust scattered in the inner solar system is like a haze that prevents you from seeing the faintest emissions from the universe,” he said.

New Horizons can use its far point to map the cosmic background in light and ultraviolet wavelengths, yielding data that cannot be gathered from the inner solar system.

“We’re going to be doing maps of the entire sky in ultraviolet, and we’re going to look at selected regions in the optical, to try and make sense of these two background signals, which already tell us from the initial observations that there is at least one source of unknown light coming from extragalactic space,” Stern said. Or from cosmology.” “And then, finally, we will also map the local interstellar medium in hydrogen light, to understand cloud structures and other structures that have not been mapped before.”

New Horizons isn’t going to run out of horizons anytime soon, suggested Becky McCauley Wrench, a program scientist in the Division of Planetary Sciences at NASA Headquarters.

“The Planetary Science Division and the Heliophysical Science Division are coordinating on the future of the New Horizons mission,” she said. As part of that, Heliophysics plans to bring out RFI [request for information] In the near future to understand the possibility of achieving science.