Before NASA’s planetary defense probe DART crashes into the asteroid Demorphos next week and self-destructs, we’ll only see the sixth asteroid we’ve ever seen up close.
Scientists are eager to get their hands on these images. Because they admit how little we know about the potential threats that space rocks pose. earth.
Mission asteroid Full of surprises. Almost two years before September 26th darts NASA learned firsthand how unpredictable these space rocks are when they collide. OSIRIS-REx mission briefly lands on asteroid Bennu Collect samples. Contrary to all expectations, the boulder-strewn surface of the 0.3-mile-wide (0.5-kilometer) asteroid was so soft that it almost swallowed the probe, sent shivers down the spine of the spacecraft controller, and left a huge wall of debris. was sent into space. Using DART (short for “Double Asteroid Redirection Test”), NASA sent spacecraft to alter the asteroid’s orbit. osiris rexEncounter.
“DART will be the first mission to study a binary asteroid system up close,” said Deputy Instrument Scientist at DART’s Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO) and at the Johns Hopkins Applied Physics Laboratory. planetary scientist Terik Daly said. He told Space.com that he will manage NASA’s DART mission.
Related: NASA’s DART asteroid impact mission will be a critical test of planetary defense
Sixth space rock ever seen in detail
DART aims at the 520-foot-wide (160-m) asteroid Dimorphos, which orbits a larger 2,560-foot-wide (780 m) asteroid called Didymos. From ground measurements, scientists know how fast Dimorphus orbits Didymos and have a rough idea of the chemical composition of larger asteroids. But DART’s ultimate target, Dimorphus, is a total unknown.
“Dimorphus is small enough that it hasn’t really been studied in detail separately from Didymus,” Daly says. “We know it’s separate, but we know very little about its shape. We don’t know if Dimorphus is elongated or spherical. Is it a single rock or a pile of rocks? I don’t know.”
Thanks to the DART mission, Demorphos will become one of the best-studied asteroids in the world. universejoin OSIRIS-REx target asteroid Bennu, Itokawa When Ryugu Asteroids visited by Japanese missions Hayabusa 1 When Hayabusa 2 and the Eros An asteroid explored by NASA’s NEAR Shoemaker probe in the early 2000s. Dimorphus and Didymos would only be her sixth and her seventh cosmic rocks ever seen up close by a spacecraft, and the 26,000 currently known to approach Earth’s orbit regularly. It is one of more than one asteroid. In addition to the above four Asteroid Tutatis Chinese came briefly Chang’e 2 The lunar rover that took multiple images in 2012.
Unpredictable collision effects
The spacecraft will transmit images of the asteroid captured by the DRACO camera at a rate of one per second, before the DART slams into the surface of Demorphos at a staggering speed of 13,680 mph (22,015 kph). First, the camera recognizes both asteroids, then focuses on Dimorphus and guides the DART. As the DART lunges toward a small space rock, the view becomes more and more detailed until transmission suddenly stops at the moment of impact.
Cubesat made in Italy called ricia cubeTraveled as a DART passenger, but released 11 days before the crash, observed the crash from a safe distance of 600 miles (1,000 km) and zoomed onto the newly scarred surface to study the crash in detail. increase.
Scientists know very little about Dimorphus, so we don’t know how the rock will react to DART attacks. Will the asteroid be as soft as Bennu and engulf DART like a swamp, or will it become a hard piece of rock that completely flattens her van-sized DART? gravity It’s so weak that looking at rocks from above doesn’t help predict impact effects.
“Images can be deceiving. Unless you touch [the asteroid]you don’t know,” said Patrick Michel, principal investigator at the European Space Agency (ESA). hera missionwill visit Dimorphos and Didymos in 2027 to finish investigating the aftermath of the impact, ESA said at a Sept. 15 press conference.
“The reason is that you are in a very low-gravity environment,” added Michel, a planetary scientist at the University of the Côte d’Azur in France. we experience on earth. ”
What is Demorphos made of?
Based on the way Didymus, the larger of the two rocks, reflects light, astronomers believe the asteroid is mostly rich in silicates, unlike Bennu, which is made of less dense carbon-rich material. I think it’s made out of rock.
If Dimorphus is made of the same material as its larger brethren, and our assumptions are correct, collisions with DART could be less random and less efficient in altering Dimorphus’ trajectory than if the asteroid were softer. said Daly. But we’ll have to wait for LICACube data to know for sure.
CubeSats will also flyby around Dimorphus, showing the entire asteroid so scientists can reconstruct its shape. However, it will take weeks or months to download all the data and uncover her Dimorphos secrets.
How do binary asteroids form?
The Didymos-Dimorphus duo is the first binary asteroid to be studied in detail, so scientists hope to learn something about how these cosmic rock couples form. According to estimates, about 16 percent of near-Earth asteroids wider than 650 feet (200 m) may be binary stars. Asteroid triplets are also known to exist. According to some theories, such asteroids could form when a larger rock begins to rotate so quickly that some of its material sloughs off in the process, he said. said. Other theories suggest that binaries and triplets may be produced in collisions.
“And one of the things that the DART mission can do is look at what Didymos looks like in an image, and what Dimorphos looks like in an image,” Daly said. “And if they are similar, that is, very similar in brightness, have a similar kind of morphology, it suggests that Didymus and Dimorphus may have split. Didymus If it turns out to be more similar than Bennu but Dimorphus looks like one rock in the universe, this splitting approach might not make sense.
Asteroids are full of surprises, and seeing one doesn’t predict the behavior of all others. But learning as much as possible about Didymos and Dimorphus will help scientists make better guesses about other asteroids, Daily said. And the more we know, the more likely we are to do things right when dangerous space rocks set their sights on Earth.
Follow Tereza Pultalova on Twitter @TerezaPultarova. follow us on Twitter @space.com and Facebook.
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