Earth Defense: the Dart spacecraft will hit an asteroid tonight for an experimental mission

After ten months of travel, NASA’s Dart probe will cross paths with Dimorphos at 1:14 tonight. Objective of the experiment: to test a device to change the orbit by impact to protect our planet from this threat in the sky.

The encounter itself seems incredible, the collision, after a ten-month journey and 11 million kilometers from Earth, of a half-ton spacecraft, Dart, with a rock almost 160 m in diameter which traverses the solar system at several thousand kilometers per hour. But the skill is covered by the stake. In this case, anticipating a potential disaster, “one of the natural risks we can control”Aurélie Moussi, astrophysicist at CNES, the National Center for Space Studies.

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

An inventory of near-Earth cruisers

To this end, at 1:14 the next night, Dart will collide at full speed with Dimorphos, the satellite of an asteroid named Didimos. An object close to the Earth, one of the celestial objects orbiting the solar system, such as the Earth, some of which contain, for life, a potential mortal danger.

“Those that are considered very dangerous, more than a kilometer in diameter, are listed, we have about 1,200, explained Aurélie Moussi. They are tracked from Earth, but the chance of an impact is very small, on the order of once every 500,000 to a million years. But from a hundred meters in diameter, they can do a lot of damage. “ More than 4,000 have been inventoried, one third of which is well-known, identifies the astrophysicist, frequent observation campaigns are carried out to refine this cataloging.

A very small difference, maybe 1%

Didymos and “Didymoon”, its small satellite, belong to what we know and the path of the couple does not represent any danger for the Blue Planet. Even deflected, which is what Dart will have to deal with tonight. Autonomous, making its descent with its camera, the Dart will strike the Dimorphos “at 6.1 km per second”24,000 km/h explained Nancy Chabot, of NASA during this same press briefing: “It will only cause a small change, maybe 1% of its orbit (around Didymos, editor’s note) but this little change” may, if proved, be fundamental.

?The latest episode of The Incredible Adventures of the #HeraMission it’s out!

Next Tuesday, @NASAof #DART mission is the ‘Crater Making’ of Dimorphos #asteroid to be studied by ESA’s Hera mission. Find out how and why in the latest episode?

— ESA (@esa) September 22, 2022

The distances traveled are such, in space, that even a modest change in orbit would be enough to make a substantial shift in arrival and avoid a catastrophic impact. The idea of ​​scientists is that this test will begin “Validate a deflection technique that we can apply to any other asteroid”, planned by Ian Carnelli, head of the Hera mission (ESA), to go in 2026 to observe immediately the consequences of this night’s “contact”. But before that, early response a little after one in the morning under the gaze of the Italian cubesat Licia, without missing a crumb.

A rather interesting celestial couple

there “a bonus in this mission”, smiled Aurélie Moussi, for astrophysicists. The couple Dimorphos – Didymos was chosen for reasons related to the test: “We need a near-Earth asteroid, approaching Earth on a date relevant to the mission. And by impacting smaller, you don’t risk putting the duo in a new and threatening path.” But this pair of “travelers” has another interest: “This is the first time we’ve visited a double asteroid.”

Scientists have many questions about this. “How do they hold, how do they form, what do they do?”, lists the doctor of astrophysics, who is involved in the Hera mission group that manages the two cubesats that will accompany the spacecraft. What feeds researchers’ impatience – “There are always surprises in asteroids!” – and justify a sleepless night!

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