Using a propulsion engine that wouldn’t look out of place in “Star Trek,” the Psyche probe travels to a cosmic iron mass

1. NASA recently collected material from the asteroid Bennu and then sent that space probe to the asteroid Apophis. Why does the organization still want to go to asteroid Psyche?

Rocks like Bennu and Apophis are the remaining blocks of the basin in which Earth and the other planets formed 4.5 billion years ago. With pristine sediments within them, these rocks could help reveal the history of our solar system.

However, Psyche is composed of about 30 to 60 percent iron, and is therefore very different from ordinary rocks like Bennu. Iron planets like Psyche appeared a little later in the cosmic timeline, and thus could help color another period of our cosmic history.

When space rocks clump together to form protoplanets, a type of planet in the making, their internal composition changes. During assembly, the protoplanet becomes so hot that the components inside it melt. Because metals like iron are heavier, they then sink to the center of the protoplanet.

This is why planets like Earth have an iron core. Larger asteroids, such as Vesta, the third-largest space rock in the asteroid belt between Mars and Jupiter, also have an iron core.

But Psyche — which stumbles through the same asteroid belt — is, as mentioned, largely composed of metal. Psyche is more than 200 kilometers in diameter, and is roughly half the size of Vesta. It has an irregular shape similar to a potato.

Astronomers suspect that this iron mass is the impact-prone core of a (primordial) planet that broke apart early in the solar system’s history and lost its rocky material from the outside.

Because scientists can’t easily drill to reach our Earth’s iron core — which lies roughly 2,900 kilometers below the Earth’s surface, while the current deep drilling record is just over 12 kilometers — Psyche offers an excellent opportunity to explore a similar environment.

Hence there is a possibility that when the probe reaches its destination in 2029, scientists will discover that the assumptions about Psyche are wrong.

For example, from Earth it appears as if Psyche contains a few iron oxides, compounds common to the four Earth-like planets (Mercury, Venus, Earth, and Mars). This suggests that this particular iron block may have a different, more unique cosmic history.

2. What kind of research will the space probe conduct?

The Psyche probe, including solar panels roughly the size of a tennis court, contains several instruments to map the features of asteroid Pysche. It will take different measurements from August 2029 to November 2031.

For example, a so-called magnetometer on the probe will check whether Psyche still has a residual magnetic field. Since planets like Earth also have their own magnetic field, this would provide a strong clue to the theory that the asteroid is the core of a shattered protoplanet.

The probe also contains spectrometers and cameras that can map the chemical composition of the asteroid, its minerals, and the age and shape of the surface.

Finally, the probe contains radio communications equipment. Based on the answer to the question of how long radio signals travel, the probe’s orbit around Psyche can be accurately determined on Earth. With this data, the effect of the asteroid’s gravity on the probe can be calculated.

From this gravity one can also infer the asteroid’s mass and rotation, and thus (indirectly) learn more about the internal structure of this cosmic iron mass.

3. Does the spacecraft do anything else?

The probe is traveling with a test of a new deep space communications system, far beyond the moon’s orbit. The goal is to more easily transmit high-resolution images and videos from distant cosmic destinations to Earth.

To this end, the system uses laser light instead of radio signals. NASA hopes to use this technology when the organization sends astronauts to the neighboring planet Mars in the distant future.

According to NASA, this new communication method should eventually be able to transfer data about ten to one hundred times faster. Because it is a test, this device has not yet been used during this mission to transmit measurement data and images taken by the probe to its cosmic destination.

During this mission, NASA will also test a new type of space engine, called a Hall effect engine. This is the first time this specific technology has been tested in deep space. Previously, the European Smart-1 mission, launched in 2003, was the only one to reach the Moon with similar engines.

The new thruster converts energy collected from the probe’s solar panels into magnetic fields on the back. With these magnetic fields, they emit charged particles (more specifically: xenon ions) fast enough to generate thrust.

The effect of this looks like science fiction: behind the engine an optical bluish glow is created that would not be out of place in fantasy space stories such as star Wars to Star Trek.

The power of the motor is modest: about the same force as an AA battery exerts on the palm of your hand. But in the cosmic depths, where vacuum-induced friction is virtually absent, this is enough to eventually achieve a steady but sustained acceleration of the spacecraft to about 200,000 kilometers per hour relative to Earth.