When an asteroid closes in on Earth, we have a rare opportunity to learn what it's made of

Gravity calculations can provide a lot of information about a variety of phenomena. Everything from Einstein’s rings to the rocket equation depends at least partially on gravity. Now an undergraduate student and a team of professors at MIT think they have a new use for gravity calculations – understanding the interior density of asteroids.

The research stemmed from a course offered at MIT known as “Essentials of Planetary Science”, which, like all good courses in a similar vein, focused at least in part on the formation of objects in the system. solar. It also included a semester final project, so familiar to many students.

In this case, one of the undergrads in the class, Jack Dinsmore, who is now a graduate student at Stanford, wanted to answer a simple question with his final project – does an asteroid do anything when it passes simply by the earth? After some preliminary modeling based on other equations taught in planetary science class, it turns out that the answer is yes.

Details about the project caught the attention of Julien de Wit, the planetary science teacher who was teaching the class. To carry out his project, Dinsmore wrote code to model what happened to the orbital and rotational dynamics of an asteroid as it passed near Earth. According to his calculations, this was mainly determined by the shape, size and, above all, the density of the asteroid.

Density is key in these calculations because it can help determine what asteroids are made of. This would partly be interesting for would-be asteroid miners. But more importantly, it is also useful to know if you want to deviate from one.

NASA recently did this successfully with the DART mission. However, many asteroids are “piles of rubble” – essentially a pile of rock held loosely together by gravity. If you stick a probe into one of them, it certainly won’t make as much of an orbital shift as hitting a solid metal section.

So where you hit an asteroid and how dense it is on its surface can have a significant impact on the effectiveness of any potential redirect mission. There are some asteroids where this information could be incredibly useful – like Apophis, which, while not posing an immediate threat to Earth, is undoubtedly one in the medium to long term.

Apophis will also prove to be a great test of the theory as to whether this modeling system will work to predict the shape and density of asteroids. It will have a close encounter with Earth in 2029, and Dinsmore and de Wit hope interested astronomers, both amateur and professional, will collect enough data on it to be able to compare it to additional simulations they have developed for a wide variety of sizes. , shapes and densities of asteroids.

This type of modeling is quite common in other fields – where scientists develop a series of models based on different quantities and determine which one best suits the data collected on a real object. With these comments, researchers should be able to determine what the interior of any asteroid would be like during a close encounter with Earth. All the more reason to keep an eye out for near-Earth asteroids that might be of interest.

Learn more:
MIT – Method for decoding asteroid interiors could help target asteroid deflection missions
Dinsmore & de Wit – Constraining asteroid interiors through close encounters
UT – Astronomers look “inside” an asteroid for the first time
UT – Upcoming asteroid mission will be able to peer 100 meters below the surface

Main picture:
Artist’s rendering of the recently completed DART mission to redirect an asteroid.
Credit – NASA/John Hopkins APL