Defense of the Earth: the Dart spacecraft will collide with an asteroid tonight for an experimental mission

After ten months of travel, NASA’s Dart spacecraft will cross the highway to Dimorphos at 1:14 am tonight. Objective of the experiment: to test an impact orbit modification device to defend our planet from this celestial threat.

The encounter itself seems incredible, the collision, after ten months of travel and 11 million kilometers from Earth, of a half-ton spacecraft, Dart, with a stone barely 160 m in diameter that crosses the solar system at several thousand kilometers per hour. However, the skill is masked by the gamble. In this case, anticipating a potential cataclysm, “one of the only natural hazards we can protect ourselves against”slides Aurélie Moussi, astrophysicist at Cnes, the National Center for Space Studies.

“It’s a world first”said a few days ago Ian Carnelli, responsible for the mission, during a press conference organized by the European Space Agency. “A truly historic moment for the entire worldadded his NASA colleague Tom Statler, a researcher at the Defense Coordination Office, the US agency’s planetary defense department.. Planetary defense is a global issue that requires a global response, and asteroids are a threat we can prevent.”

An Inventory of Near-Earth Cruise Ships

To do this, at 1:14 the next morning, Dart will collide at full speed against Dimorphos, the satellite of an asteroid called Didymos. An object near the Earth, one of those celestial objects that orbit in the solar system, like the Earth, some of which constitute for it, for life, a potential mortal danger.

“Those that are considered very dangerous are listed, more than a kilometer in diameter, we have about 1,200, Aurélie Moussi explains. They are being tracked from Earth, but the chance of an impact is very low, on the order of once every 500,000 to a million years. But from a hundred meters in diameter, they can cause considerable damage.” More than 4,000 have been inventoried, a third of them are well known, indicates the astrophysicist, carrying out constant observation campaigns to refine this cataloging.

A very small difference, maybe 1%

Didymos and “Didymoon”, its small satellite, belong to those we know well and the trajectory of the pair does not represent any danger to the Blue Planet. Even diverted, which is what Dart will tackle tonight. Autonomous, making the descent from him using his camera, Dart will hit Dimorphos “at 6.1 km per second”24,000 km/h explained Nancy Chabot, from NASA during this same press conference: “It’s only going to cause a small change, maybe 1% of its orbit (around Didymos, editor’s note) but this slight inflection” It will be, if proven, fundamental.

?The last episode of The Incredible Adventures of #HeraMission it’s out now!

Next Tuesday, @POT‘s #missionDART is ‘Create a crater’ on the Dimorphos #asteroid which will be studied by ESA’s Hera mission. Find out how and why in the latest episode. pic.twitter.com/Rqr2vGA111

— THAT (@that) September 22, 2022

The distances traveled are such, in space, that even a very modest variation in orbit can be enough to create a considerable change on arrival and avoid a tragic impact. The idea of ​​scientists is therefore with this test to start “validate a deflection technique that we can apply to any other asteroid”, projected Ian Carnelli, head of the Hera (ESA) mission, which will go in 2026 to observe the consequences of tonight’s “contact” on the spot. But first, a prompt response shortly after one in the morning under the gaze of the Italian cubesat Licia, who does not miss a single crumb.

A rather intriguing heavenly couple

There are “a bonus to this mission”, smiles Aurélie Moussi, for astrophysicists. The pair Dimorphos – Didymos was chosen for reasons related to the test: “We needed a near-Earth asteroid, which approaches Earth on a mission-relevant date. And by hitting the smaller one, there’s no risk of putting the duo on a threatening new trajectory.” But this pair of “travelers” has another interest: “This is the first time we will visit a double asteroid.”

Scientists have many questions about it. “How do they hold together, how did they form, what are they made of?”, lists the doctor in astrophysicism, involved in the Hera mission group in charge of the two cubesats that will accompany the spacecraft. What fuels researchers’ impatience – “there are always surprises with asteroids!” – and justify a sleepless night!

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