Is the asteroid Psyche really a hunk of mostly metal? Is the object, which is nearly as wide as Massachusetts, the core of a baby planet whose rocky outer layers were knocked off during a cataclysmic collision in the early days of the solar system?
Right now, all that astronomers can say is maybe, maybe not.
NASA launched a spacecraft on Friday morning, also named Psyche, on a journey to the asteroid belt between Mars and Jupiter to find out.
“We’re really going to see a kind of new object, which means that a lot of our ideas are going to be proven wrong,” said Lindy Elkins-Tanton, a professor of earth and space exploration at Arizona State University who serves as the mission’s principal investigator.
Being proven wrong, she added, “is, I think, the most exciting thing in science.”
That voyage in search of answers kicked off Friday at 10:19 a.m. Eastern time. Falcon Heavy, the largest of SpaceX’s operational rockets, lifted off from Kennedy Space Center in Florida, sending the massive spacecraft into space.
Friday’s flight overcame early, unfavorable weather forecasts for a seemingly flawless flight. Just over an hour after the launch, the Psyche spacecraft detached from the upper stage of the Falcon Heavy rocket. NASA’s video stream showed the vehicle sailing into the darkness beyond the Earth, setting off on an excursion that will last about six years and cross billions of miles.
About five minutes later, the mission’s managers applauded in the control room at NASA’s Jet Propulsion Laboratory facility in California as they received an initial signal from the spacecraft.
The asteroid named Psyche has long been a curious enigma. Spotted in 1852 by Annibale de Gasparis, an Italian astronomer, it is named for the Greek goddess of the soul, and it was just the 16th asteroid to be discovered. In the early observations, it was, like the other asteroids, a starlike point of light that moved in an orbit around the sun, and not much more.
Beginning in the 1960s, astronomers found in telescope observations that the color of Psyche was similar to iron meteorites that have fallen on Earth, said Jim Bell, a professor of earth and space exploration also at Arizona State University who will lead studies of the asteroid with the spacecraft’s camera instrument. Astronomers bounced pulses of radar off Psyche, and the reflections coming back to Earth were brighter than those that came from other small objects in the asteroid belt.
“It became pretty clear that there’s some component of the surface that’s very radar reflective,” Dr. Bell said. “And the simplest way to do that is with metallic fragments.”
And then when scientists observed Psyche passing relatively close to larger worlds, its orbit was deflected in a way that suggested something quite massive, and potentially much denser than rock.
Most rocks like granite have a density of two to three grams per cubic centimeter. Water, whether liquid or ice, is about one gram per cubic centimeter. Metals like iron are much denser, between six and nine grams per cubic centimeter.
“Some of those early estimates were like, wow, this is really quite unusual,” Dr. Bell said.
Psyche appeared to be almost pure metal. Earth’s core is made of iron and nickel, and the measurements of Psyche gave rise to the thought that it could be the remnant of a similar core that belonged to a baby planet. Such worlds are known as planetesimals, where temperatures are high enough that denser metals melt and fall to the center.
It is impossible to explore the core of a planet like Earth 1,800 miles below the surface, but going to Psyche could provide more information about what is at the center of our planet.
Or that hypothesis could be completely wrong.
“Psyche could be something entirely different than that,” Dr. Elkins-Tanton said. “I would love to be totally surprised.”
More recent measurements have led to lower estimates of the asteroid’s density, a bit less than four grams per cubic centimeter: still denser than rock and ice, but not as dense as metal. That suggests Psyche is made of metal plus something else: perhaps rock, perhaps empty space.
“My best guess is that it’s more than half metal based on the data that we’ve got,” Dr. Elkins-Tanton said.
If Psyche turns out to be full of valuable metals, it is too far away for anyone to mine using current technologies. Dr. Elkins-Tanton notes that even at its closest, Psyche is some 150 million miles from Earth, which is about five times as far as Earth is from Mars at the two planets’ closest possible approach.
The Psyche mission was scheduled to launch a year ago. The spacecraft had already been shipped to the Kennedy Space Center. But there were problems testing the navigation software that would guide the spacecraft through the solar system. These stemmed from incompatibilities between the flight software and the programs used to check it. Engineers ran out of time to work out the issues before the launch window closed.
An independent review of the missed launch, commissioned by NASA, concluded that leadership changes, communication failures, heavy workloads and the Covid-19 pandemic contributed to “an environment in which missions such as Psyche did not receive the attention necessary to deal with the staffing and experienced-personnel challenges they were facing.”
The project got back on track for 2023 by hiring new mission staff, minimizing remote work and implementing other recommendations from the review.
There were other bumps on the way to the launchpad. Psyche was scheduled to lift off on Oct. 5, but the launch was delayed again when tests revealed that thrusters used to orient the spacecraft during flight, which fire cold nitrogen gas, produced higher temperatures than expected. NASA officials said they had resolved the issue by planning to run the thrusters at lower power levels to prevent them from overheating in space.
Once it launches, the Psyche spacecraft will head toward Mars, swinging by the red planet in May 2026 and using its gravity as a slingshot toward Psyche the asteroid, arriving in August 2029 after traveling 2.2 billion miles.
During its journey, Psyche will exchange laser messages with Earth as part of an experiment called Deep Space Optical Communications. Current spacecraft communicate using radio waves, but switching to lasers could increase the bandwidth of deep space transmissions by as much as 100 times. The laser experiment will provide the first demonstration of this novel technology at distances far beyond the moon.
When it reaches the asteroid, the spacecraft will spend at least 26 months in orbit, studying Psyche with a variety of instruments.
The mission’s cameras, known as multispectral imagers, will offer the first close-up look at Psyche, revealing surface features that cannot be observed from Earth. A magnetometer aboard the spacecraft will search for signs of an ancient magnetic field, perhaps similar to the one powered by Earth’s core, which may be imprinted in the asteroid’s terrain.
And a gamma-ray spectrometer will detect high-energy gamma rays and neutrons that are forged when cosmic rays slam into the asteroid’s surface. These particles contain information about the composition and distribution of metal and rock across Psyche’s otherworldly landscape.
Finally, the spacecraft’s radio antenna will be used to map the asteroid’s gravity field by measuring slight shifts in the frequency of the Doppler shift of signal, rising as it moves toward Earth, falling when it is moving away. The experiment can detect differences in density in the asteroid, which could shed light on its origin.
“No single instrument by itself will tell us whether Psyche is a core,” Ben Weiss, the mission’s deputy principal investigator, said in a news briefing on Thursday. “It’s the combined data from all these different instruments.”
For more than 170 years, Psyche has been a small blip of light in the sky. Telescopes have revealed tantalizing glimpses of its dimensions and features, but the nature of this unique world is otherwise a mystery. The Psyche spacecraft is now on its way to bring this asteroid into sharp focus for the first time, and to solve the riddle of its origin.
