Last week’s successful launch of NASA’s mission to Psyche — a largely unknown metal-rich asteroid at the outer edge of the main asteroid belt — may soon give up its secrets. First discovered in 1852, Psyche is thought to be composed primarily of iron, nickel, and silicates, and may have been the exposed nickel-iron core of early planets (the building blocks of the first planets in the Solar System).
With the help of Johns Hopkins University’s Applied Physics Laboratory’s in-house gamma ray and neutron spectrometer, the chemical constituents of the soul should be detected with greater precision.
Measuring only about 280 km across, the spacecraft will provide clues as to whether Psyche is the center of a disconnected planetary core that has a dynamo, a mechanism that generates a magnetic field.
Once the NASA spacecraft arrives at Psyche in August 2029, the spacecraft will orbit the asteroid at a distance of about 700 km over the next two years, according to the Planetary Science Institute in Tucson. From there, it will gradually approach the planet as its instruments map the surface and search for evidence of an ancient magnetic field.
Core formation requires heat and melting, as the dense metal cores separate from the silicates and descend toward the core of the body, Thomas Prettyman, a Psychiatric Associate Researcher at the Institute for Spherical Sciences, tells me via email. He suggests that the planet’s internal heat source may be the decay of short-lived radioactive isotopes produced in nearby supernovae.
As radioactive isotopes decay, the core cools, creating a core, mantle and crust, says Prettyman. The outer silicate layers may have been removed by impacts exposing the core, he says. This may have happened even when the core was still partially molten.
If it’s a relic of a planet, it’s likely to be one of the oldest bodies in our solar system, Prettyman notes.
How does a gamma ray and neutron spectrometer instrument work?
As cosmic rays and high-energy particles bombard the asteroid’s surface, the elements there absorb the energy, NASA says. In return, they emit neutrons and gamma rays of different energy levels.
The spectrometer analyzes the asteroid’s fundamental energy emission, which the team then matches with the emission characteristics of known elements on Earth. This will help detect specific elements on the asteroid’s surface.
The detector relies on the rare element germanium to detect the gamma rays emitted by the element.
Germanium is a relatively dense (or heavy, high atomic number) element, which effectively stops gamma rays, APL planetary scientist and physicist David Lawrence tells me via email. When gamma rays stop in germanium, the 'stopping energy’ of the gamma rays creates an electrical signal that can be measured by high-precision electronics.
If there’s too much iron and too much nickel, it can give signs of a prominent appearance, says Lawrence. The true value of nickel abundance (high or low) may indicate how it may have formed and/or differentiated.
After all, at some point in its early history, the internal structure of the psyche 'separated’ into separate layers, usually the structures of a core, mantle and crust.
I expect elements like iron, silicon, aluminum, calcium, and oxygen in the rock, says Lawrence. A high level of sulfur indicates an interesting volcano.
About detecting an ancient magnetic field?
Heat-driven rotation of the conducting liquid metal inside the core likely created a strong magnetic field, says Prettyman. As the core freezes from the outside, the outer layers become magnetized, preserving a record of the dynamo that can be detected by the spacecraft’s magnetometer. If the core is still molten when the outer layers are removed, inward solidification is more likely, he says.
In 2030, when the spacecraft reaches a low-altitude orbit around Psyche, we will begin collecting our primary science data in about 100 days, says Lawrence. We expect to have a good understanding of Psyche’s composition in late 2030 or early 2031.
„It took years to develop and perfect the engineering needed to design these detectors for planetary missions (which require low mass, low power),” says Lawrence.
What’s so exciting about taking data into the soul?
„When we do our initial testing, the first opportunity for 'excitement’ will be less than two months,” says Lawrence, who is particularly interested in seeing if there is an abundance of detectable nickel in Psyche.
We’ve flown by or encountered many asteroids, but it’s a mystery, Rosalie Lopes, associate director of the Planetary Science Directorate at NASA’s Jet Propulsion Laboratory, tells me via email.
Who knew what grooves would look like in the metal world? Could there be metallic lava flow at the surface?
„I think the surface is mind-blowing,” says Lopes.
„Oddany rozwiązywacz problemów. Przyjazny hipsterom praktykant bekonu. Miłośnik kawy. Nieuleczalny introwertyk. Student.