One of the least intriguing objects in the solar system is without a doubt Dimorphos. This rock, or moonlet, is approximately 160 metres (525 feet) across and orbits the dwarf asteroid Didymos, which is only 780 metres in size (2,560 ft). The Didymos-Dimorphos system, which is situated 11 million kilometres (6.8 million miles) from Earth, is only a small portion of the river of debris that orbits the sun in the asteroid belt between Mars and Jupiter.
On the other hand, Dimorphos will be the focus of much of the astronomical community’s attention on Monday, September 26 at precisely 7:14 p.m. ET. At that time, the NASA DART spacecraft would purposefully strike the moonlet in the snout while travelling at a speed of around 28,200 kph (kilometres per hour) (17,500 mph). By destroying or deflecting asteroids before they can cause the kind of catastrophic damage that occurred when a space rock crashed off the Yucatan Peninsula 65 million years ago, triggering the global extinction event that resulted in the extinction of the dinosaurs, NASA and other space agencies around the world may be able to protect the planet from incoming asteroids.
The present-day Earth is in actual danger. Near-Earth asteroids (NEAs), which are defined as space debris that is not trapped in the asteroid belt but orbits the sun in a way that gets it within 45 million kilometres (28 million miles) of Earth, are kept track of by NASA’s Center for Near Earth Object Studies (CNEOS). Although it would appear to be a fairly safe miss distance, there is always the possibility that another piece of space debris in free flight could run into an NEA, altering its trajectory and directing it in our direction. According to the CNEOS census, there are more than 10,000 known NEAs that are at least 140 m (460 ft) across and 855 known NEAs that are at least 1 km (.62 mi) across. The CNEOS database contains 29,801 known NEAs of all sizes.
Our best protection against NEAs is intercepting and deflecting them, thus on November 23, 2021, NASA launched DART in an attempt to test this as-yet-unproven strategy. Actually, there are two spacecraft involved. The primary DART body is 2.6 m (8.5 ft) broad and 600 kg in weight (1,320 lbs). It is accompanied by a little spacecraft the size of a toaster created by the Italian Space Agency (ISA), known as the Light Italian CubeSat for Imaging Asteroids (LICIACube). The task of LICIACube, which broke away from DART on September 11, is to fly close by and take pictures of the moonlet before and after impact. DART itself will collide with Dimorphos.
In a statement from NASA, LICIACube navigation director Dan Lubey said, “We are working with ASI to get LICIACube to within 25 to 50 miles [40 to 80 km] of Dimorphos just two to three minutes after DART’s impact—close enough to get good images of the impact and ejecta plume, but not so close LICIACube could be hit by ejecta.
When it comes to accumulating data on the kind of physical harm an impactor spacecraft can inflict on an asteroid, LICIACube’s work will be crucial. But measurements of how significantly DART alters Dimorphos’ orbit around Didymos will serve as the true test of the mission’s success. Numerous Earth-based telescopes, notably the NASA Deep Space Network of radio telescopes at Barstow, California; Madrid, Spain; and Canberra, Australia, will be used to answer that question.
DART would likely shorten the moonlet’s 11.9-hour orbital period around Didymos by a few minutes, according to NASA’s current best guess. Even a tiny adjustment in an asteroid’s speed or trajectory when it is millions of kilometres away from Earth could cause it to fly well wide of us when it ultimately approaches our planetary neighbourhood, thus despite what might seem to be a small shift, it is actually a very significant one.
The universe has always been perilous. It might be safer with the support of the DART mission. As early as next week, it will be clear exactly how much safer.