A NASA spacecraft is on course to deliver material from an asteroid to Earth—here’s what we could learn

Round 15 years in the past, I used to be on a European Space Agency (Esa) committee, Esa’s technique for proposed forthcoming space missions. Into consideration was a mission to an asteroid. Over dinner, one of many committee members, an astrophysicist, quizzed me on why we would have liked to go to considered one of these objects.

“NASA has already been to 1 and the Japanese Area Company to a different. Why do you have to go to a different one? They’re all the identical aren’t they, simply lumps of rock?” My intentionally less-than-polite response was: “Why do astronomers preserve eager to launch extra telescopes into space to have a look at stars? They’re all the identical aren’t they, simply balls of burning fuel?” Our meal continued in frosty silence.

The misunderstanding that asteroids are “simply lumps of rock” does not stand as much as scrutiny, given the wealthy harvest of details about asteroid variety that has come from learning meteorites. Meteorites have taught us in regards to the origin and evolution of the solar system.

We are able to measure the ages of meteorites and determine the volatiles—water- and carbon-containing chemical compounds—that some comprise. Volatiles are essential for understanding how the constructing blocks of life had been delivered to Earth.

However there are gaps in our data, so we have to research samples instantly taken from asteroids—partially as a result of meteorites are sometimes contaminated with compounds from Earth’s atmosphere. This implies we won’t at all times make sure that the volatiles in them got here from the asteroid itself, or from Earth.

We additionally do not absolutely perceive the connection of particular meteorite varieties to totally different courses of asteroids. This impacts our understanding of how volatiles had been distributed within the early solar system and due to this fact what varieties of objects may have delivered life’s constructing blocks to Earth. Therefore the necessity for pattern return missions.

On Sunday 24 September, a NASA spacecraft referred to as Osiris-Rex will fly previous Earth and launch a capsule containing a haul of dust and rock, which it collected from the floor of the asteroid Bennu in 2020. Under the watching eyes of nervous scientists, the capsule will parachute right down to a take a look at vary in Utah, the place it is going to be retrieved and brought to a sample-curation facility in Houston.

A wealthy heritage

The earlier missions talked about by my astrophysicist colleague had been NASA’s Near-Shoemaker spacecraft, which operated from 1996 to 2001, and the Japanese space agency’s (Jaxa) Hayabusa mission, which lasted from 2003 to 2005.

Hayabusa introduced a couple of milligrams of fabric to Earth from the asteroid Itokawa. This allowed us, for the primary time, to measure an asteroid’s age –- an essential first step in understanding relationships between asteroids and meteorites.

The 2 most up-to-date asteroid missions are Jaxa’s Hayabusa2 mission to the asteroid Ryugu and NASA’s Osiris-Rex mission to Bennu. The missions each orbited carbonaceous asteroids, that are wealthy in volatiles. The orbiting spacecraft helped verify that Ryugu and Bennu are each water-rich asteroids, with ample clay and carbonate minerals.

The asteroids have very low densities, suggesting they’re objects referred to as “rubble piles.” These comprise important quantities of empty space beneath the floor. Rubble piles shaped from particles thrown into space when their larger dad or mum our bodies had been hit by one other object. The rubble ultimately got here collectively to kind an asteroid of its personal.

Watery historical past

Outcomes from evaluation of samples from Ryugu had been printed in December 2021. They confirmed that the Ryugu materials could be very related in composition to what we name CI meteorites. That is essential as a result of CI-related supplies are extraordinarily fragile and simply weathered.

Consequently, few survive their passage by way of the Earth’s environment. Now that we will hyperlink these uncommon meteorites extra definitively to the category of asteroids Ryugu belongs to, we will increase our understanding of the processes that asteroids went by way of as they advanced.

Previously, temperatures on some asteroids had been simply excessive sufficient for liquid water to exist. The response of the unique minerals with water remodeled them into extra advanced mixtures. Evidence suggests the dad or mum asteroid for Ryugu was altered by water between two million and 5 million years after the solar system shaped.

An essential purpose of Hayabusa2 was to research organics (carbon-containing chemical compounds) within the pattern. There’s overlap between organics and volatiles. Each classes embody compounds that would have been essential for the origin of life.

There have been round 20,000 species (varieties) of organic compound present in the Ryugu material. This opened our eyes to the sheer complexity of natural compounds in primitive asteroids.

So what’s nonetheless left to be taught from Bennu? For a begin, Osiris-Rex noticed vivid areas on Bennu’s floor. These had been interpreted as thick veins of the mineral carbonate.

These weren’t seen on Ryugu’s floor, though particular person grains had been discovered throughout lab analysis of the samples. This might counsel that alteration by water passed off underneath totally different circumstances on Bennu.

If the ages of alteration by water are totally different between Ryugu and Bennu, it may imply one of many asteroids underwent an extended means of alteration. This may counsel that their dad or mum our bodies shaped in numerous elements of the solar system.

Like Ryugu, Bennu could be very darkish. Analysis of Ryugu from orbit recommended {that a} course of referred to as space weathering could have helped darken and dehydrate the asteroid’s floor. Nonetheless, lab evaluation of the Ryugu pattern revealed the presence of clay minerals, displaying that water was in actual fact ample on the asteroid. If the identical impact is noticed for Bennu, there are implications for the seek for water on asteroids.

Bennu is acknowledged as a probably hazardous asteroid, which means there’s a one in 3,000 probability of it hitting us in 150–200 years’ time.

By the point the worldwide neighborhood of planetary scientists has analyzed all of the out there materials from Bennu, it’s unlikely that any side of its formation, evolution and orbital historical past, composition and elements will likely be unknown, permitting an efficient “Earth rescue” mission to be launched.

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