The control programs of ESA and NASA of those that could potentially hit us and future missions. In all, 1,449 objects are kept under observation
As of March 8, 2023, there are 1,167,079 asteroids classified by ESA (European Space Agency) of which there is good orbital information, almost all in the belt between Mars and Jupiter. Of these, 31,385 (plus 119 comets) fall into the category Nea (Near-Earth Asteroids), that is, with orbits that bring them to approach a little less than 200 million kilometers from the Sun, or about 20 million kilometers from the Earth. Among them there are 1,449 which are potentially dangerousi.e. with one probability of impact on our planet very small or very remote in time, but which cannot be considered equal to zero.
The most dangerous
What are the ten most dangerous according to ESA (here the complete list)? Leading up is 2023DW, which has a one in 700 chance of colliding with Earth. Experts say, however, that these are preliminary data and that, as happened in the past with other objects, when more accurate data becomes available, its threat will be greatly reduced. In second place there is 2001VB, apparently much more dangerous because the date of the close encounter is next July 23rdo (at 9.16 am Italian time), but the probability of the impact is only 1 in 356 million, very low.
I paragoni
They are all very small objects, up to an estimated diameter of up to 400 metres, the vast majority with diameter of a few tens of metersthe. For comparison, Arizona’s Meteor Crater was formed 50-60 thousand years from the impact of a 100-meter-diameter metallic asteroid that caused a 180-meter-deep hole with a diameter of 1,300 meters. The one that exploded on February 15, 2013 at a height of 30 kilometers above the Siberian skies of Chelyabinsk (causing about 1,500 lightly injured by shards of broken glass due to the displacement of air from the explosion with an energy comparable to that of 35 atomic bombs such as that of Hiroshima) had a diameter of 20 meters and weighed 13,000 tons.
L’asteroide Bennu
Then there are two larger objects, including the asteroid Bennu, included in a special list because, given their size, they are much more menacing even if the dates of their possible impacts are moved into the future by several centuries. After new studies, the most probable date of Bennu’s impact has been placed at 24 September 2182 with a 1 in 2,700 probability, i.e. with a 99.963% probability that it will pass close by but without any devastating impact.
Between Neo and Pho
This does not mean that these “orbiting stones” should not be monitored carefully. Even NASA has its own list of potentially dangerous asteroids (which it calls Neo, Near-Earth Objects, including asteroids and comets). Among them are the Pho (Potentially Hazardous Objects), with diameters of at least 140 meters and orbits that come within 7.5 million kilometers of Earth. NASA currently has a list of 2,990 Phos. To be dangerous, however, not only the approach distance is necessary, but there must be the possibility that the orbital plane of the asteroid intersects that of the Earth. Conversely there can be no collisions.
How to defend ourselves
Apart from the list of objects under observation, how can we protect ourselves from an object destined to strike us? To avoid ending up like the dinosaurs, hit 66 million years ago by the effects of an impact with an asteroid 10 kilometers in diameter, space agencies have launched various experimental programmes. According to scientists, launching a nuclear warhead missile against the asteroid would be of little use, as well as being dangerous it would also be counterproductive. The best idea is to deviate, even slightly, the orbit. In practice, push it a little to the side. On September 26, 2022, NASA’s Dart mission managed for the first time to change the orbit of Dimorphos, a small rock that orbits the asteroid Dydimos, demonstrating that this system can be successful. In 2026 NASA will launch the new infrared space telescope Neos (Near-Earth Object Surveyor) which will have the task of facilitating the identification of these potential threats. ESA is planning the Neomir mission in 2030, with the same objectives.
The next
So what’s next to pass us by? It’s 2020FV4, pebble of 30 meters in diameter which will pass on Monday 13 March. But 6.7 million kilometers away. The next day there will be 2023CM with a diameter of 190 meters: it will pass at 3.94 million kilometers.
March 9, 2023 (change March 9, 2023 | 18:12)
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