Astronomers have discovered the most detailed map of the Psyche of the metal asteroid

Astronomers have discovered the most detailed map of the Psyche of the metal asteroid

If you want to do a forensic study of the solar system, you might head to the main asteroid belt between Mars and Jupiter. There you can find ancient rocks from the early days of the solar system. There in the cold vacuum of space, far from the Sun, asteroids are mostly untouched by space weather.

Space scientists sometimes refer to asteroids – and their meteorite fragments falling to Earth – as time capsules because of the evidence they possess.

The asteroid Psyche is especially interesting, and NASA is sending a mission to investigate an unusual piece of rock.

Prior to that mission, a team of researchers combined Psyche observations from a series of telescopes and constructed a map of the asteroid’s surface.

Astronomers divide asteroids into three categories. Carbon or C-type asteroids are the most common type. They make up about 75 percent of known asteroids and contain large amounts of carbon. Carbon makes them dark, and they have low albedos.

Silicate 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 metals than other types of asteroids, and scientists think 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 miles) in diameter. It is called 16 Psyche because it was the 16th discovered smaller planet. (Larger asteroids like Psyche are also known as smaller planets.)

(NASA / JPL-Caltech / ASU)

The psyche is sometimes called the “gold mine asteroid” because of the richness of iron and nickel it contains. Although let’s be clear, no one thinks he is rich in gold.

Visible light images of the Psyche do not tell us much. The VLT of the European Southern Observatory took some pictures of the asteroid, but did not reveal any details.

The history of the Psyche is the history of uncertainty. Astronomers have long thought that this discovered iron core was a much larger body. In this hypothesis, a strong collision or a series of collisions separated the bark and mantle of the body.

The larger body would be completely differentiated and would have a diameter of about 500 km (310 miles). As the bark and mantle disappeared, only a core rich in iron remained.

The idea fell out of favor as time went on and astronomers continued to observe it. Evidence has shown that it was not thick enough to make solid iron and that it was probably porous.

Other researchers have suggested that the psyche is somehow disturbed and then re-created as a mixture of metals and silicates. One study showed that Psyche is not as rich in metals as thought and is more of a pile of rubble. In that scenario, collisions with more frequent type C asteroids deposited a layer of carbon and other materials on the surface of the Psyche.

The most exotic idea behind Psyche’s origin is the ferro-volcanic idea. A study from 2019 presented evidence that Psyche was once a molten stain. In that scenario, the outer layers cooled and formed stress cracks, and a floating molten core erupted like iron volcanoes.

The only way to know for sure what Psyche is is to go and look at it. So that’s what NASA is doing.

The mission is called Psyche and is planned to be launched sometime in the fall of 2022. The spacecraft will rely on solar-electric propulsion and gravity maneuver with Mars to reach Psyche in 2026.

He will spend 21 months studying the asteroid and will follow four separate orbital paths, each one closer to the previous one.

Illustration of the Psyche probe near the Psyche asteroid. (NASA / JPL-Caltech / ASU)

As it approaches the asteroid, it will focus on various scientific goals.

A team of researchers constructed a new map of Psyche’s surface to help prepare for the mission.

The map is in a paper published in Journal of Geophysical Research: Planets. The title is “Heterogeneous Surface of the Asteroid (16) Psyche”, and the main 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’s an evolved surface, and these maps confirm that metal-rich asteroids are interesting enigmatic worlds. That’s 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 get a better look at 16 Psyches. ALMA is a radio telescope composed of 66 high-precision antennas. Separate antennas work together as a high-resolution interferometer.

ALMA works on wavelengths sensitive to temperature and some electrical properties of materials on the surface of the Psyche.

“ALMA antenna signals can be combined into a synthetic signal equivalent to a 16-kilometer (10-mile) telescope,” said co-author Catherine de Kleer, assistant professor of planetary science and astronomy at Caltech. “The bigger 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 its ambient temperature. Higher thermal inertia means it takes longer.

The second is the dielectric constant. The dielectric constant describes how well a material conducts heat, electricity, or sound. The material with a low dielectric constant conducts poorly and is a good insulator and vice versa.

Researchers took ALMA observations of thermal inertia and dielectric constants and performed hundreds of simulations to see which combinations of materials could explain them. “We conducted 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 the Psyche, researchers were able to map the surface and locate regions richer in iron. Iron also has a high thermal inertia because it is so dense.

So, combining measurements of thermal inertia and dielectric constant gives a good idea of ​​which parts of the surface of the Psyche are rich in iron and other metals.

Researchers call an interesting feature of Psyche the Bravo-Golf region. This region has systematically lower thermal inertia than mountain regions. The Bravo-Golf region is a depression to the right of the asteroid’s prime meridian in the image below.

Why does an area at low altitude have lower thermal inertia? Other studies show that the region is also radar bright. Why is that? Researchers have come up with three possibilities.

Lowlands may be rich in metals, but covered with fine, porous regolith that reduces their thermal inertia compared to plateaus covered with coarser regolith. Thermal inertia increases with particle size. In this scenario, finer regolith would gather in the lowlands.

“Ponds of fine-grained materials have been seen on small asteroids, whose gravity is small enough to hit an earthquake and cause finer materials to collect,” said Cambioni. “But the Psyche is a big body, so if the fine-grained materials have accumulated at the bottom of the depression, this is interesting and a bit mysterious.

Another hypothesis is that the surface material covering the lowlands is more porous than the plateau. Thermal inertia decreases as the porosity of the rock increases. Impact cracks could also make the lowlands more porous.

The third hypothesis is that lowlands have more silicate-rich materials than plateaus, which gives them a lower dielectric constant than some plateau areas. The idea is that the Bravo-Golf depression could have been caused by the impact of a silicate-rich impact element and left behind silicate-rich remnants.

All in all, the study shows that the surface of 16 Psyche is covered with a large number of different materials. This also adds other evidence showing that the asteroid is rich in metals, although the abundance of metals and silicates varies significantly in different regions.

He also suggests that the asteroid could be the remnant of a core of a differentiated body that has long since lost its mantle and crust.

“In conclusion, we provide evidence that Psyche is an asteroid rich in metals whose surface is heterogeneous, shows both metallic and silicate materials and appears to have evolved by impact,” the authors conclude.

Simone Marchi is a scientist at the Southwestern Research Institute and a co-researcher at NASA’s Psyche mission. Marchi was not included in the study, but commented on its importance in a press release. “These data show that the surface of the Psyche is heterogeneous, with possible remarkable variations in composition. One of the primary goals of the Psyche’s mission is to study the composition of the asteroid’s surface using its gamma rays and neutron spectrometer, and color imaging device. something the Psychology Science Team wants to study more. “

It will be up to NASA’s Psyche mission to more rigorously confirm these findings.

But sending a spaceship all the way to the Psyche to understand it in more detail is something more than the Psyche itself.

If Psyche is a backward nucleus 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 we expect to be in the Earth’s core? The earth’s core is not dense enough to be pure iron and nickel. Scientists believe that it contains lighter elements such as sulfur, silicon, oxygen, carbon and hydrogen.

The Psyche mission will also determine whether the asteroid formed under conditions of higher oxidation or reduction than the Earth’s core. That will tell us more about the solar nebula and the protoplanetary disk.

People sometimes call Psyche a gold mine asteroid because it is so rich in metals. An object of its size would contain a huge amount of iron, although it is unlikely that this value will be realized or available soon.

But if knowledge is as valuable as iron, then Psyche 16 could still be a gold mine.

This article was originally published by Universe Today. Read the original article.

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