NASA’s DART asteroid launched two million pounds of rocks into space
The massive tail from the collision of a spacecraft and an asteroid earlier this year opens up key information about space rocks – and how to manage any rock that might one day threaten Earth.
NASA’s Double Asteroid Redirection Test (ArrowThe mission crashed into a small space rock called Dimorphos in late September in preparation for the possibility that humans might one day want a distraction. asteroid on a collision course with Land. Within weeks of the impact, the DART team announced that the impact shaved 32 minutes of Dimorphos’ orbit around its larger companion, Didymus — in the high range of the team’s pre-launch estimates. Scientists are now sharing additional findings about the impact during the American Geophysical Union’s annual conference, which is being held this week in Chicago and online.
“DART has been a tremendous success,” Tom Statler, DART mission program scientist, said during a press conference held Thursday (December 15) to coincide with the meeting. “I’ve seen these results, and I know they’re absolutely amazing.”
Related: See the first images of the wild DART asteroid crash!
Many of the new findings focus on the startling, cometLike the tail generated by the debris from the collision. Mission scientists weren’t sure in advance how much debris the DART collision would create, but the impact didn’t disappoint.
And scientists had a front row seat, thanks to the DART spacecraft’s Italian passenger, Light Italian Cubesat for imaging asteroids (LICIACube), which was equipped with two cameras and deployed 15 days before the DART impact, allowing it to fly over Dimorphos just three minutes after impact. Images of the tiny spacecraft show quite a cosmic chaos, with clouds of material exploding from space rocks.
“The images were really cool,” said Alessandro Rossi, a LICIACube science team member and scientist at the Instituto di Fisica Applicata Nella Carrara in Italy, during the press conference. “We didn’t expect some of the features we’re seeing.”
Scientists are still analyzing the LICIACube data, but the images captured with it two cameras It can provide an idea of the size of the particular debris, how fast it is traveling, and more, Rossi said. Researchers think they can see the debris casting a shadow on the larger asteroid Dimorphos orbiting it, Didymos.
The debris provides a sense of the asteroid’s structure, since an asteroid of solid rock will produce much less ejecta than an asteroid made of rock clumped together—picture bouncing a tennis ball on the pavement compared to throwing it in a sandbox.
In addition, the shell solved a major mystery about Dimorphos and Didymos. Scientists suspected the two space rocks would be made of similar material, but they had no way to test that theory, either when the spacecraft blasted off to their destination or using ground-based telescopes, none of which are powerful enough to see them. Dimorphos directly.
Before the collision, scientists could have used the light they saw from the system to analyze the composition of the space rock pair in general, knowing that almost all of that light came from Didymos. But in similar data taken just after the collision, flying debris from Dimorphus is responsible for most of the light.
A comparison of the two light signatures showed that although some slight differences were visible, the material looked quite similar between the asteroids. “We’re very excited to see that these two objects are actually very similar in composition,” Christina Thomas, a planetary scientist at Northern Arizona University who leads the DART observations working group, said during the press conference.
Scientists will study New Dimorphus tail For a long time, including delving into observations taken in the days after the collision, collecting new data to see how the plume changes over time, and comparing observations from different observation points.
“We have a view of the output shaft at close range, we have a view from the ground, we have a view from Hubble Space TelescopeFrom James Webb Space TelescopeRossi said. So we have a lot of different geometries to compare to, and this allows us to clearly distinguish the projectile plume from many points of view. “
Crush the numbers
During the press conference, the scientists also shared two key numbers they’ve calculated since the collision.
First, they began to estimate the amount of flying debris from the asteroid: at least 2.2 million pounds (1 million kilograms), and possibly as much as 22 million pounds (10 million kilograms). Given the total mass of Dimorphos to be perhaps 11 billion pounds (5 billion kg), the rock may have lost only 0.2% of its material, even if the higher estimate proves correct.
“We’re talking about a very small fraction,” Andy Rifkin, a planetary scientist at Johns Hopkins Applied Physics Laboratory and co-chair of DART, said at the press conference.
Number two goes to the core of the DART mission objective. DART wasn’t about seeing inside an asteroid, it was about orbiting it Planetary defense. This involves searching for asteroids in orbits that cross Earth and calculating whether the two objects might find themselves in the same place at the same time.
If scientists one day discover a large asteroid that poses a real threat, the reasoning is, humans could try to intervene by speeding up the asteroid’s orbit around the sun Until he misses his appointment with Earth. DART tested one technique for this, called kinetic impact — a fancy name for hitting an asteroid with a heavy, fast-moving object.
However, scientists don’t have a good sense of how the properties of the asteroid and the collision will interact to cause a specific change in the momentum of rocks in space, making it difficult to know what size spacecraft to launch, for example.
Scientists use an important number called The “momentum transfer factor” or beta, to describe the effectiveness of the asteroid impact. If a spacecraft hits an asteroid head-on in a collision that doesn’t produce any debris, the space rock will pick up exactly the momentum the spacecraft had when it crashed, which is beta 1.
A range of characteristics can influence the beta factor — whether a spacecraft hits a soft patch or a large rock, say, the asteroid’s internal structure, and what material the asteroid is made of — but let’s put it aside for simplicity’s sake.
Debris that shoots off the asteroid and reaches space gives the asteroid additional momentum, which gradually increases the beta factor of the impact. Scientists have now calculated the beta factor for the effect of DART at 3.6. This value means that the asteroid picked up more than three times more momentum than it would have in its clean impact, and that debris from the impact impacted the asteroid more than the spacecraft itself.
“This is very good news for kinetic impact technology,” Andy Cheng, lead of the DART investigation team at Johns Hopkins Applied Physics Laboratory, said during the press conference. “At least in the case of the DART, the kinetic impact on the target was really effective at changing the target’s orbit.”
The calculation also gives scientists much-needed real-world data to understand how an asteroid’s properties affect momentum transfer—data needed to determine how large a kinetic spacecraft’s impact is to avert catastrophe. The successor to DART, the European Space Agency Hera spacecraftcurrently scheduled for launch in 2024, will also play a major role here after arriving (more gently) at the asteroid pair to study Dimorphos and Didymos up close.
“What we’re trying to get at is having this ability to observe an asteroid, either from Earth or perhaps on a reconnaissance mission, and infer what the response would be like if we deployed a kinetic impactor against it,” Statler said.
Despite the interesting results regarding both science and planetary defence, the mission team stressed that they did not finish the project.
“From here, now, we actually get to our dream slate where we can start to think about the really complex dynamical effects that were predicted, that we weren’t sure we could observe because we wouldn’t be looking forward to more observations that will allow us to study things,” Thomas said. In great detail, and I think that’s a really cool place to be.”
Email Megan Bartels at firstname.lastname@example.org or follow her on Twitter @mbartelsMegan Bartell. Follow us on Twitter @Spacedotcom and on Facebook.
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