ASU sensor will help NASA’s Lucy mission solve solar system riddle



South West Research Institute

Artist illustration of the Lucy concept.

On Saturday, NASA launched its Lucy mission to study Jupiter’s Trojans – clusters of asteroids that precede and follow the gas giant orbiting the Sun.

A sensor built by ASU will help the mission settle an ongoing debate about the origins of the solar system.

Montage data from planets surrounding distant stars reinforces the idea that our sun’s planets did not form in their current orbits, but instead migrated to and away from the sun in the distant past.

“With these patterns of migration of the planets, early in the history of the solar system, it was a pretty crazy place. And the planets were moving and things were being thrown out, even scattered out of the solar system,” said Phil Christensen of ASU’s Earth and Space School. Exploration, which leads the Lucy Thermal Emission Spectrometer (L’TES) team.

If this is true, then the makeup of the Trojans should reflect icy origins far beyond the orbit of Neptune.

This is because the Trojans were trapped long ago in special pockets where the sun’s gravity balances perfectly with that of Jupiter.

These areas, where gravitational and centripetal forces balance each other out, are called Lagrange points.

“It’s like this gravitational hole that you fall into and can’t get out of. So they collected things,” Christensen said.
But Trojans are more than old – they are pristine.


NASA / WMAP scientific team

At Lagrange points, the gravitational pull of two large masses is exactly equal to the centripetal force required for a small object to move with them. The Trojans are located in the L4 and L5 of Jupiter.

Many asteroids, including Bennu, the target of OSIRIS-REx, at one point approached closer to the sun, which baked their surfaces and altered the thawing, motion, and re-freezing of volatiles such as l ‘water.

But Trojans have occupied their Lagrange points since the beginning of the solar system.

“So they’ve never been heated. They’ve never been bathed. And so they’re really, really primitive material – not just old, but primitive. It hasn’t been altered since it came down. is condensed for the first time four and a half billion years since. “

The TSES is the latest in a long line of thermal emission spectrometers that Christensen teams have launched on board missions such as Europa Clipper, Mars Global Surveyor and OSIRIS-REx. Some of their instruments are still working 20 years after their launch.

This tally was a major influence on what NASA asked them to deliver.

“They wanted an infrared instrument, but they wanted something that wouldn’t cause them any problem, it’s been proven, you know. And we did, ”Christensen said.

Christensen said he doesn’t mind reproducing his pride and joy. For him, that makes more sense than working to perfect a technology and making just one copy.

“I joke with people about, you know, imagine somebody made an iPhone, and they just made one. It’s like, wow, that was a lot of work for one,” did he declare.

Lucy will study the major Trojans in 2027 and the tail group in 2033, with flyovers of Earth in between.

Because the spacecraft will search for some of the earliest remnants of the solar system, it is named after one of the most famous hominid fossil skeletons studied on Earth. This Lucy was found in Ethiopia in 1974 by Donald Johanson and Tom Gray.

Suitably enough, the Lucy spacecraft will fly over Main Belt asteroid (52246) Donaldjohanson en route to Jupiter.

Christensen said he looks forward to any surprises lurking among the floating fossils of Troy.

“You’re always surprised. You know, we’re going to go out and say, ‘Oh, that’s not what we thought.’ That’s the beauty of doing it, ”Christensen said.


South West Research Institute

Lucy’s orbital path (green) relative to Jupiter. After launch, Lucy made two close flyovers of Earth before encountering her L4 Trojan targets from 2027 to 2028. After diving beyond Earth again, Lucy will visit L5 targets in 2033.


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