by Any day now, it could happen: We could detect an asteroid on an Earth-crossing trajectory. It could be a small one; it could be a big one. It could be tomorrow; maybe a thousand years from now. So what can we do about it?
We know that rocks of all shapes and sizes have hit World many since its inception. We see evidence of it on the moon: All those craters preserve a record of the damage. On our planet, craters are rare, but that’s because wind and water erode the evidence of recent craters, and plate tectonics takes care of the older ones.
Based on evidence from crater and observational records an asteroid population, we can put together a general picture of how often disaster occurs in our world. Every few years, hits about a dozen meters across our planet. When it does, it releases the energy equivalent of a reasonably sized nuclear bomb. But most of those explode in the upper atmosphere over open oceans, so we don’t usually notice them.
Related: How many potentially dangerous asteroids does the Earth miss each year?
On the larger side, kilometer-scale asteroids hit Earth about every 10 million years. They have the potential to cause global catastrophe — it didn’t work out too well for the dinosaurs. Fortunately, while these massive space rocks are destructive, they are extremely rare.
In between those extremes is the sweet spot of danger: large asteroids that could wipe out a city or destroy a civilization – by far the biggest disaster to ever happen to us. Those kinds of things hit Earth every few thousand years. And those are the ones we need to worry about.
Track and protect
So far, the International Astronomical Union’s Minor Planet Center, which tracks these types of objects, has counted 34,152. near-Earth objects (NEOs), which are asteroids whose orbits bring them within 0.05 astronomical units (AU) of Earth’s orbit. (One AU is about 150 million kilometers, or 93 million miles—about the average distance between Earth and the sun.) These NEOs are not necessarily threats—the vast majority are almost always far away from Earth— but they are certainly threats. we have to keep a close eye on him.
This catalog comes from a collection of ground-based observatories and i spacewhich was usually borrowed, extra time. But to come Vera C. Rubin Observatory it will give a big boost to NEO detection, as it will continuously monitor the sky, providing a complete catalog every few nights. Astronomers expect that with this observatory, we will identify between three and 10 times the number of NEOs currently known.
But recognizing these things is only one piece of the puzzle. We also need to know where the asteroids are headed, which requires tracking their movements night after night. And you can’t just monitor for a few nights and call it a day; asteroids have a bad habit of changing their orbits frequently. This is due to its small, irregular size. Small gravitational tugs from the giant planets can change their trajectories, as passes can close with each other. Even their color and shape make a difference: Depending on the asteroid’s reflectivity and spin rate, the Sun it can unevenly heat the surface of the space rock, causing a small but constant change in momentum.
Only through rigorous, continuous monitoring can we confidently identify any potential threat to our home.
Big guns
That’s part one of logic planetary protection strategy. Part two is doing something about the threat.
One option is to do nothing: Let the object hit Earth and hope it doesn’t do too much damage. That’s not very attractive, so we can take a more active approach.
If we find the asteroid early enough, we can push it out of its current orbit. NASA demonstrated the feasibility of this approach with the the success of the Double Asteroid Redirect Test (DART) mission.in which a simple spacecraft slammed headfirst into Didimosthe small moon of the asteroid Démorphos. The influence drive measurable change i didymos orbitsuggesting that we might be able to pull off this stunt in the event of a real threat.
If slamming headfirst seems too aggressive, we can also adjust the asteroid’s orbit in more subtle ways. A “gravity tractor” could send a spacecraft into orbit around an asteroid; that the spacecraft would slowly change the direction of the asteroid, and that its gravitational influence would also change the direction of the asteroid. We could also paint the threatening rock, which would indicate a different amount of sunlight on one side, which would also change its orbit.
Related Stories:
—8 ways to stop an asteroid: Nuclear weapons, paint and Bruce Willis
—If an asteroid really threatened Earth, what would a planetary defense mission look like?
—Protecting the Earth from asteroids is complex and requires global cooperation
The key to making all this work is early detection. If we see the asteroid too late, we won’t be able to provide it with enough energy to change its course. We might be able to change where in the world the object hits – for example, we could try to aim it over the open ocean – but that’s the best we can hope for.
Therefore, when it comes to preventing the worst disaster that humanity could see, we must keep our eyes on the sky, patient and alert to danger.
