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How NASA’s Mission to Bennu Will Keep Earth Safe from Asteroids



The concept of the artist of OSIRIS-REx which collects a sample from Bennu.
Illustration: NASA Goddard Space Flight Center

NASA's OSIRIS-REx mission will not only make beautiful photos of the asteroid Bennu, but will also help scientists learn if one day the rock threatens Earth.

There are many reasons to study asteroids. They could be potential mines for precious resources like water and heavy elements, and they contain clues that we can study to learn how it was the Solar System in its early days. But even the big things that hit the Earth can have catastrophic consequences. Even scientists are interested in this.

Bennu is a 1,600-foot-wide asteroid that orbits the Sun relatively close to the Earth. OSIRIS-REx, NASA's mission to study it, was launched in September 2016 and arrived at its target last Monday. The spaceship carries five instruments: a camera suite, a LIDAR system (such as radar, but with a laser instead of radio waves) and three spectrometers, which measure different wavelengths of light to determine the composition dell & # 39; asteroid.

Bennu is particularly important when it comes to our own survival. About every six years, it comes relatively close to the Earth ("close" in cosmic terms, but far from any other measure). The models suggest that during its close proximity between the years 2175 and 2196, it has a 1 in 2,700 chance of colliding with us. This is still incredibly small (a 99.963% chance of losing), but Bennu is a big rock, even the exaggerated odds are too big to ignore when civilization is at stake.

Why astronomers do not know for sure if we are sure? There are many forces at play, and small differences can change the odds. During some close approaches of the asteroid, the Earth's gravity will give it a push that could move it on a collision course. Furthermore, there is the Yarkovsky effect, according to a press release by Jet Propulsion Lab: the irregular warming of the Sun on such a light body can cause changes in its trajectory. It is not clear where Bennu will go after 2135.

OSIRIS-REx and the telescopes on Earth will continue to characterize the asteroid, tracing its path and determining how gravity and the Yarkovsky effect will influence its trajectory . We hope the mission will produce trajectories 60 times more accurate than current estimates, according to the press release.

So what happens if Bennu becomes a threat? Well, you personally should not worry, because the chances are very good that you're dead. Even your children will probably be dead (the American life expectancy is falling, so do not tell me it's a sure thing that we'll live longer in the future). But researchers are working on some solutions. A mission called the Double Asteroid Redirection Test will attempt to slam a spacecraft into an asteroid to cause a change in trajectory. Perhaps we could atomize the asteroids. Or, if we have enough delivery time, perhaps we can simply paint one side to change the way it absorbs solar radiation, using the Yarkovsky effect to our advantage.

There is a lot of data to gather before you know what Bennu and many other interesting sciences will do. But know that Bennu is not the asteroid you should worry about. The asteroids that should worry about are those that have not yet been detected.

[NASA JPL]


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