If you want to do a forensic study of the solar system, you can take the trip to the main asteroid belt between Mars and Jupiter. This is where you can find ancient rocks from the early days of the solar system. Out there in the cold vacuum of space, far from the sun, asteroids are largely untouched by space weathering.
Space scientists sometimes refer to asteroids – and their meteorite fragments that fall to Earth – as time capsules because of the evidence they have.
The asteroid Psyche is particularly interesting, and NASA is sending a mission to investigate the unusual catfish.
Ahead of that mission, a team of scientists combined observations of Psyche from a series of telescopes and constructed a map of the asteroid’s surface.
Astronomers divide asteroids into three categories. Carbonaceous or C-type asteroids are the most common type. They make up about 75 percent of known asteroids and contain large amounts of carbon. The carbon makes them dark, and they have low albedos.
Silicon-containing or S-type asteroids are the second most common type. They make up about 17 percent of known asteroids and are mostly made of iron and magnesium silicates.
Metal or M-type asteroids are the rarest types of asteroids and make up about 8 percent of known asteroids. They appear to contain more metal than the other asteroid types, and scientists believe they are the source of iron meteorites falling to Earth. M-type meteorites were one of the earliest sources of iron in human history.
Psyche (16 Psyche) is an M-type asteroid. It is also called a dwarf planet because it is about 220 kilometers (140 mi) in diameter. It is referred to as 16 Psyche because it was the 16th smaller planet to be discovered. (Larger asteroids such as Psyche are also known as smaller planets.)
Psyche is sometimes called the ‘gold mining asteroid’ because of the richness of iron and nickel it contains. Although it should be clear, no one thinks it is rich in gold.
Visible slides of Psyche do not tell us much. The VLT of the European Southern Observatory took some pictures of the asteroid, but they did not reveal any details.
The story of the psyche is a story of uncertainty. For a long time, astronomers believed that it was the exposed iron core of a much larger body. In this hypothesis, a powerful collision or series of collisions removed the body’s crust and mantle.
The larger body would have been completely differentiated and measured approximately 500 km (310 miles) in diameter. With the crust and mantle gone, only the iron-rich core remained.
That idea fell into disfavor as time went on and astronomers continued to observe it. Evidence showed that it was not dense enough to be solid iron and is probably porous.
Other researchers suggested that Psyche was disturbed in some way and then rebuilt as a mixture of metals and silicates. A study indicated that Psyche is not as rich in metal as expected and is more of a pile of stones. In that scenario, collisions with more common C-type asteroids deposited a layer of carbon and other materials on Psyche’s surface.
The most exotic idea behind Psyche’s origins is the ferro-volcanic idea. A study from 2019 presented evidence that Psyche was once a molten blob. In that scenario, the outer layers cooled and formed stress cracks, and the liquid molten core erupted like iron volcanoes.
The only way to find out for sure what Psyche is is to go and look at it. So that’s what NASA does.
The mission is called Psyche and is scheduled to be launched sometime in the autumn of 2022. The spacecraft will be dependent on solar-electric propulsion and a gravitational assistance maneuver with Mars to arrive at Psyche in 2026.
It will spend 21 months studying the asteroid and will follow four separate orbits, each successively closer than the previous one.
As it moves closer to the asteroid, it will focus on various scientific objectives.
A team of researchers constructed a new map of Psyche’s surface to prepare for the mission.
The map is in an article published in Journal of Geophysical Research: Planets. The title is “The Heterogeneous Surface of Asteroid (16) Psyche”, and the lead author is Saverio Cambioni from MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).
“The surface of the psyche is very heterogeneous,” Cambioni said in a press release. “It is a developed surface, and these maps confirm that metal-rich asteroids are interesting enigmatic worlds. There is another reason to look forward to the Psyche mission going to the asteroid.”
In this study, the authors used the Atacama Large Millimeter / Submillimeter Array (ALMA) to look better at 16 Psyche. ALMA is a radio telescope consisting of 66 high-precision antennas. The separate antennas work together as a high-resolution interferometer.
ALMA operates at wavelengths that are sensitive to temperature and some electrical properties of materials on the surface of the Psyche.
“The signals from the ALMA antennas can be combined into a synthetic signal equivalent to a 16-kilometer (10-mile) telescope,” said co-author Katherine de Kleer, assistant professor of planetary science and astronomy at Caltech. “The larger the telescope, the higher the resolution.”
The new map is based on two types of measurements. One is thermal inertia, which is how long it takes for a material to reach ambient temperature. Higher thermal inertia means that it takes longer.
The second is the dielectric constant. The dielectric constant describes how well a material conducts heat, electricity or sound. A material with low dielectric constant conducts poorly and is a good insulator and vice versa.
The researchers took the ALMA observations of thermal inertia and dielectric constant and ran hundreds of simulations to see what combinations of materials could explain them. “We ran these simulations area by area so that we could capture differences in surface properties,” says Cambioni.
Pure iron has an infinite dielectric constant. By measuring the dielectric constant on Psyche, the researchers were able to map the surface and locate areas that are richer in iron. Iron also has high thermal inertia because it is so dense.
So combining thermal inertia and measurements of dielectric constant gives a good idea of which surface areas of the Psyche are rich in iron and other metals.
Researchers call a strange feature about Psyche for the Bravo-Golf region. That region has a systematically lower thermal inertia than the highland regions. The Bravo-Golf region is the depression just to the right of the asteroid’s main meridian in the image below.
Why does a low-lying area have lower thermal inertia? Other studies show that the region is also radar light. Why? The researchers came up with three possibilities.
The lowlands can be rich in metal, but covered with fine, porous regolith which lowers their thermal inertia compared to the highlands covered with coarser regolith. Thermal inertia increases with particle size. In this scenario, fine-grained regolith would have accumulated in the lowlands.
“Ponds of fine-grained materials have been seen on small asteroids, whose gravity is low enough for shocks to shake the surface and cause finer materials to accumulate,” said Cambioni. “But the Psyche is a large body, so if fine-grained materials accumulate at the base of the depression, this is interesting and a little mysterious.”
The second hypothesis is that the surface material covering the lowlands is more porous than the highlands. Thermal inertia decreases as the porosity of the rock increases. Impact fractures can also make the lowlands more porous.
The third hypothesis is that the lowlands have more silicate-rich materials than the highlands, which gives them a lower dielectric constant than some areas of the highlands. The idea is that the Bravo-Golf depression could have been formed by a blow with a silicate-rich impact force and left silica-rich residues.
Overall, the study shows that the surface of 16 Psyches is covered by a large selection of materials. It also adds other evidence showing that the asteroid is rich in metals, although the amount of metals and silicates varies considerably in different regions.
It also suggests that the asteroid may be a remaining nucleus of a differentiated body that lost its mantle and crust long ago.
“In conclusion, we provide evidence that Psyche is a metal-rich asteroid whose surface is heterogeneous, shows both metal and silicate materials, and appears to have evolved by shock,” the authors conclude.
Simone Marchi is a staff researcher at the Southwest Research Institute and a co-researcher on NASA’s Psyche mission. Marchi was not involved in this study, but commented on its significance in a press release. “These data show that Psyche’s surface is heterogeneous, with possible remarkable variations in composition. One of the main objectives of the Psyche mission is to study the composition of the asteroid surface using gamma rays and neutron spectrometers, and a color imager. So, the possible presence of compositional heterogeneities something that the Psyche Science Team is eager to study more. “
It will be up to NASA’s Psyche mission to confirm these findings more strictly.
But sending a spacecraft all the way to Psyche to understand it in more detail is about more than just Psyche itself.
If Psyche is the remaining core of a rocky, differentiated planetesimal, it will reveal something about our planet and how differentiated bodies are formed. Will it contain some of the same light elements that we expect to be at the core of the earth? The earth’s core is not dense enough to be pure iron and nickel. Researchers believe it contains lighter elements such as sulfur, silicon, oxygen, carbon and hydrogen.
The psyche mission will also determine if the asteroid was formed under conditions that are more oxidizing or more reducing than the Earth’s core. It will tell us more about the solar nebula and the protoplanetary disk.
Sometimes people refer to Psyche as the gold mining asteroid because it is so metallic. An item of size will contain a huge amount of iron, although that value is unlikely to be realized or available right away.
But if knowledge is as valuable as iron, 16 Psyche can still be a goldmine.
This article was originally published by Universe Today. Read the original article.