By Steve Gorman
(Reuters) -NASA on Friday launched a spacecraft from Florida on its way to Psyche, the largest of the several metal-rich asteroids known in our solar system and a body thought to be the remnant core of an ancient protoplanet.
The Psyche probe, folded inside the cargo bay of a SpaceX Falcon Heavy rocket, blasted off from NASA's Kennedy Space Center in Cape Canaveral on a planned journey 2.2 billion miles (3.5 billion km) through space. The spacecraft, roughly the size of a small van, is due to reach the asteroid in August 2029.
The launch, shown live on NASA TV, marks the latest in a series of recent NASA missions seeking clues about the formation of our planet about 4.5 billion years ago by sending robotic spacecraft to explore asteroids - primordial relics from the dawn of the solar system.
This asteroid measures roughly 173 miles (279 km) across at its widest point and resides on the outer fringes of the main asteroid belt between the planets Mars and Jupiter.
The spacecraft was due to be released from the rocket's cargo bay about five minutes after the launch, then take about two hours to unfurl its twin solar panels and point its communications antennae toward Earth.
Psyche's mission control team plans to spend the next three to four months conducting checks of the spacecraft's systems before sending it on its journey into deep space, propelled by solar-electric ion thrusters being used for the first time on an interplanetary mission.
After reaching the asteroid, the spacecraft would then orbit it for 26 months, scanning Psyche with instruments built to measure its gravity, magnetic proprieties and composition.
According to the leading hypothesis, the asteroid is the once-molten, long-frozen inner hulk of a baby planet torn apart by collisions with other celestial bodies in the early solar system. It orbits the sun about three times farther than Earth, even at its closest to our planet.
'OUTER SPACE TO EXPLORE INNER SPACE'
The first asteroid of its kind chosen for study at close range by spacecraft, Psyche is believed to consist largely of iron, nickel, gold and other metals whose collective hypothetical monetary value has been placed at 10 quadrillion dollars.
But the Psyche mission has nothing to do with space mining, according to scientists. Its objective is to gain insight into the formation of Earth and other rocky planets that are built around cores of molten metal. Earth's molten center is too deep and too hot to ever be examined directly.
"So we say, tongue-in-cheek, that we're going to outer space to explore inner space," Lindy Elkins-Tanton, Psyche's principal investigator for NASA's mission partner Arizona State University, told a briefing for reporters on Tuesday.
One of the spacecraft's primary instruments is a spectrometer to measure molecular signatures of gamma rays and neutrons emitted from the asteroid's atoms as it is bombarded by cosmic radiation from the sun, allowing scientists to map Psyche's iron composition.
Once reaching Psyche, the probe is set to circle it in a series of gradually descending orbits, ending up a mere 40 miles (64 km) from the asteroid's surface, before ending the mission in November 2031.
The asteroid, discovered in 1852 and named for the goddess of the soul in Greek mythology, is the largest of about nine known asteroids that appear from ground-based radar observations to consist largely of metal, with rocky material mixed in. Still, scientists can only guess at what Psyche looks like, Elkins-Tanton said.
The spacecraft is programmed to approach Mars in May 2026 for a gravity assist intended to boost its momentum and put its trajectory on course for its final destination.
Other spaceflight milestones in store for the Psyche mission include a ride-along technology demonstration testing a laser-based communication system to send high-bandwidth data to Earth from beyond the moon for the first time.
It also marks the first dedicated NASA launch on a Falcon Heavy rocket furnished by Elon Musk's SpaceX company, and the first interplanetary mission ever flown by the Falcon Heavy.
The launch came two weeks after NASA accomplished a return to Earth of the largest sample of material ever collected from the surface of an asteroid, in this case a much smaller, rocky near-Earth asteroid named Bennu.
NASA in 2021 launched a spacecraft named Lucy on a 12-year expedition to study the Trojan asteroids, two large clusters of space rocks orbiting the sun ahead of and behind the path of Jupiter.
And last September, NASA sent a spacecraft slamming into an asteroid with enough force to nudge it from its natural path - the first time humans altered the motion of a celestial body - in a successful test of a planetary defense system.
(Reporting by Steve Gorman in Los Angeles; Editing by Will Dunham)
