- Jonathan Amos
- BBC science reporter
The probe will only be able to discern its target for the last 50 minutes or so (the image is an artist’s work).
In the coming hours, a NASA probe will collide with an asteroid.
The aim of the probe, “DART”, is to find out how difficult it is to prevent a large rock in space from colliding with Earth.
This test is taking place about 11 million kilometers away on a target called Dimorphos.
The agency says that “the rock is not currently on the way to impact the Earth, and the test will not cause it to change direction accidentally to head to Earth.”
The collision will take place at 23:14 GMT on Monday. Telescopes will monitor this from afar, including the new James Webb Hyperspace Observatory.
We’ve all seen how Hollywood portrayed it with brave astronauts and nuclear weapons.
But how do we protect Earth from a real killer asteroid?
NASA is getting close to finding out. The idea is simply that a spacecraft collides with an asteroid.
The idea is to need to change the speed of the rock by a small amount to change its course, so that the Earth will miss – provided that this is done a sufficient distance and time in advance.
Dart’s double asteroid redirection test mission will verify this theory by almost directly colliding with the 160-meter-wide Demorphos at a speed of more than 20,000 kilometers per hour.
This should change its orbit around a much larger asteroid, called Didymus, by just a few minutes each day.
NASA promises to get some stunning images from the 570-kilogram Dart probe as it began the impact process.
picture released, HERA/ESA
The European Space Agency will continue the mission (Image is the work of an illustrator)
“The DART mission is the first planetary defense test mission to prove the effectiveness of a spacecraft collision with an asteroid in order to move its position very slightly in space,” said Dr. Nancy Chabot, who works in the Johns Hopkins University Applied Physics Laboratory, and is leading the NASA mission.
She added in an interview with the BBC: “This is what you would do years ago, if you needed, to give the asteroid a small push to change its position in the future so that the Earth and the asteroid are not on a collision path.”
And beating Demophos will be the big challenge. The Dart probe will only be able to distinguish its target Demorphos from Didymus, which is 780 meters wide, for the last 50 minutes or so.
The probe’s navigation software must then adjust the spacecraft’s trajectory to create a direct hit.
“Because of the speed of light and the distances involved, it’s not really feasible to have a pilot sitting on the ground with a joystick in the spacecraft. There isn’t enough time to respond,” said Dr. Tom Statler, a NASA Dart program scientist.
“We had to develop software that could interpret the images taken by the spacecraft, figure out the correct target and perform trajectory correction maneuvers by firing the thrusters.”
It will spin images back to Earth at a rate of one image per second as it heads toward “deep punch.” What initially appears as a point of light in the images will quickly grow to fill the entire field of view, before the feeding is abruptly cut off as the spacecraft is destroyed.
Fortunately, this is not the end of the story. It carried with it an Italian cube satellite weighing 14 kg, which was launched a few days ago. His job is to record what happens when DART digs a hole in an asteroid.
His images, taken from a safe distance of 50 km, will reach Earth in the coming days.
“The moon will pass Lyciacube about three minutes after the DART collision,” said Simone Perotta of the Italian Space Agency.
He added, “This timing was chosen to allow things to develop fully because one of the main contributions of “LichiaCube” is to document what happened and confirm the deflection of the asteroid’s orbit.”
picture released, HERA/ESA
It currently takes Demorphos around Didymus approximately 11 hours and 55 minutes. The collision is expected to change the momentum of the smaller object, reducing the orbital period to about 11 hours and 45 minutes. Telescope measurements will confirm this in the coming weeks and months.
And space surveys, along with statistical analyzes, indicate that we have identified more than 95 percent of ferocious asteroids that could begin to die out globally if they collide with Earth (and it wouldn’t happen if they calculated their trajectories and knew they wouldn’t come close to our planet). But this still leaves many little things undiscovered yet that can cause chaos, even if only on the scale of a region or city.
And if an object like Demorphos hits the ground (which it won’t), it could dig a hole perhaps a kilometer in diameter and a few hundred meters deep. The damage will be severe in the vicinity of the impact.
Four years from now, ESA will have three spacecraft – collectively known as the HERA mission – to engage with Didymos and Demorphos and conduct further follow-up studies.