On April 13, 2029, an astronomical event will occur that may not occur again for the next 10,000 years, and which will be visible in the sky to hundreds of millions of inhabitants of Europe, Africa and part of Asia. The asteroid Apophis, a rock 375 meters in diameter, will make its closest approach to Earth and will pass about 10 times closer than the Moon. It is a unique opportunity that space agencies will take advantage of to train the world’s strategy against impacts that could wipe out an entire city, or even a small country.
“Nature is doing a very valuable experiment for us; all we have to do is be there to study it,” he sums up. Paolo Martinoleader of planetary defence missions for the European Space Agency (ESA). The passage of the asteroid will be spectacular. “With a clear sky, at around 9 p.m. [hora peninsular española] and close to the horizon, Apophis will be visible as a very, very bright star that will remain in the night sky for about four hours. For the superstitious, all this will happen on a Friday the 13th,” jokes the Italian engineer.
Objects the size of Apophis — named after the ancient Egyptian god of chaos — hit Earth about once every century, Martino explains. They are comparable in energy to the explosion of several atomic bombs. Although they do not generate radioactivity, they do produce a shock wave that can be as destructive as a hurricane. The most devastating bodies are those that do not touch the ground and explode in mid-flight. “We are used to Hollywood-type scenarios in which the threat is discovered only three days in advance, but the truth is that we will probably do so years in advance, which would give us time to develop a diversion mission similar to AIDA. In the worst case, a nuclear projectile would have to be used. The strategy would not be to hit directly, because it would cause a rain of radioactive material, but to detonate the bomb close to the object to divert it,” he explains.
Martino stresses the global importance of these missions. “Unlike earthquakes or volcanic eruptions, meteorite impacts are the only natural disasters that we can predict and prevent. We don’t know when we will need to do so, but if we don’t have a plan in place, we will be in a real bind,” he points out.
If all goes well, when Apophis crosses the night sky there will be a small European probe, Ramsestravelling alongside it. The robotic craft will document, second by second, the mind-blowing effects that Earth’s gravity will have on this body: deformations, changes in speed and rotation, landslides and even earthquakes. The information it collects will be key to launching future missions to reconnoiter asteroids that are going to collide with Earth and to draw up the best deflection strategy, which will probably require the launch of a second impact probe.
Although asteroids hitting Earth seem like something out of a movie, the threat is real. The most dangerous are not the largest bodies that could cause a planetary disaster, such as Chixculub, which caused the extinction of the dinosaurs 66 million years ago. The vast majority of these objects have already been discovered and it is known that they will not hit the planet. The greatest danger is posed by smaller ones, with a diameter of 100 to 300 meters, because there are tens of thousands out there that we know nothing about.
Two United Nations committees specializing in such threats have stipulated the exact limit at which humanity should take action. If it is larger than 50 meters in diameter, a mission would have to be launched to study it and deflect it. These committees have been bringing together scientists and engineers from the main space agencies for years to discuss options and even carry out drills in response to imminent threats. Taking advantage of the arrival of Apophis, the UN wants to declare 2029 as the world year of planetary defense.
On September 27, 2022, the probe DART NASA’s refrigerator-sized asteroid — with a mass of 600 kilograms — struck Dimorph, an asteroid about 10 million times larger. It was the first dress rehearsal for NASA’s Planetary Protection Office to learn how to deflect future asteroids larger than 140 meters in diameter, which could destroy an entire city if they hit our planet.
The mission was a resounding success, as it significantly slowed down and deflected Dimorph, 160 meters in diameter. This body was chosen because it orbits like a moon around Didymus, another asteroid measuring 780 meters. After hitting head-on at about 22,000 kilometers per hour, DART It reduced Dimorfo’s orbital period by 32 minutes, which deviated it by about 35 meters, a record.
“With knowledge comes responsibility,” argues Juan Luis Cano, an aeronautical engineer at ESA’s Planetary Defence Office. “Thirty years ago we had not discovered most of the asteroids that could pose a serious risk, but now that we have, it would be absurd for our societies not to take steps to prevent them,” he points out.
In October, the 22 ESA countries, including Spain, plan to launch the mission into space Herawhich will travel millions of kilometers to reach that binary system in two years. This is a much more complicated and expensive maneuver than the one DARTbecause “it requires inserting itself into the trajectory and speed of these two bodies, which takes more time and fuel,” says Cano. The ship carries several cameras on board and will deploy two small satellites to study in detail the effects of the impact on Dimorfo, measure the crater left by the American ship and analyze the composition of this body. The information will be a treasure for calculating what to do in case a similar body threatens Earth.
Knowing the composition of the threatening body is crucial. 50,000 years ago, an object measuring around 50 metres impacted in what is now Arizona (United States), opening a crater more than a kilometre in diameter and destroying all forms of animal life within four kilometres around. In 1908, an object measuring around 80 metres fell in Tunguska, in central Russia, destroying around 80 million trees, but without touching the ground. The Arizona meteorite was metallic and survived its passage through the atmosphere. The Tunguska meteorite was much less compact and burned completely in the atmosphere without reaching the ground, causing, however, an infernal flare that devastated vegetation of an area similar to the island of Gran Canaria.
The mission Ramses will do something very similar to Hera with Apophis. The aim is to track this body before, during and after its closest approach to Earth, which puts ESA in a race against time. The launch is due in April 2028 to arrive a month and a half before its closest approach, at a distance similar to that of many geostationary satellites.
Earth’s gravity exerts a variable force depending on how close you are to its center. This basic principle is going to work wonders on Apophis. The area closest to the planet will suffer greater thrusts than the area further away, which will compress it, deform it and probably cause rock falls and even earthquakes, which will be measured by a small satellite that will have previously landed on its surface to gather key information in the event of a future threat.
If Ramses is to rendezvous with asteroid Apophis ahead of its close approach to Earth, it must launch by April 2028. We cannot wait until the next Ministerial Council to secure funding or we would lose the opportunity, thus @THAT has been approved to kick-start mission prep using… pic.twitter.com/CTC9NTBvkL
— Josef Aschbacher (@AschbacherJosef) July 16, 2024
Launch a mission like Ramses In just four years, this is a challenge that ESA has never faced before. In fact, the need to get the project up and running has already prompted a historic decision by its 22 member countries to skip the bureaucracy and start devoting money and time to designing the mission before its official approval, scheduled for the ministerial meeting in November next year. “We are paving the way for a new ESA… already Apophis,” said Josef Aschbacher, the agency’s director general, on social media.
Now two crucial tasks begin: the design of the mission and the political and diplomatic work so that, when the summit of November 2025 arrives, the member countries decide to give the green light to Ramses. Unplanned, ESA is testing its ability to carry out a reconnaissance mission in record time, a situation very similar to what would happen in the event of an imminent impact.
Although the ESA has not detailed how much money will be dedicated to the design of Ramses Nor its total cost, it is known that it wants to be somewhat cheaper than its predecessor. Herawhich cost around 300 million euros. For that price, Europe can score a goal against NASA. In April 2022, the US space agency decided to redirect its mission Osiris-Rexwhich was returning to Earth after visiting the asteroid Bennu, to deviate towards Apophis. But the lack of fuel will only allow it to arrive after the maximum approach, when the Earth’s gravity will have already worked its transformation of the asteroid, which will even change its trajectory. The information from Ramses This will be key to learning how to deflect space rocks, explains Cano: “A body the size of Apophis could completely destroy a region the size of Catalonia.”
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