An asteroid 35 million miles away was heading toward Earth, and NASA and other space agencies were faced with an alarming scenario last month. It had just been discovered after spending several months in the inner solar system. In six months, the space rock was expected to hit.
Exciting, right?
It is also completely untrue, as this was just a hypothetical scenario part of a simulated asteroid exercise designed to help the United States and international experts prepare for such a situation.
A group of students learned a difficult lesson in the simulation. If an Earth-bound asteroid were detected with just a few hours' warning, there was nothing anyone could do to stop it from hitting Earth.
Considering the six-month window for the scenario…
No existing technology can prevent the asteroid from hitting. It simply isn’t possible for a spacecraft to destroy an asteroid or push it off its course in such a short amount of time.
During the recent simulation, as well as five other simulations like it, Paul Chodas, manager of NASA's Center for Near-Earth Object Studies, assisted. Participants were made to fail in this exercise, according to him.
"It's what we call a short-warning scenario," he told Insider. "It was, by design, very challenging."
Scientists would need years, not months, of warning if an asteroid like the fictional one headed for Earth. Chodas suggests that the minimum is five years. Others, including MIT astronomer Richard Binzel, say it will take at least a decade.
"Time is the most valuable commodity you could possibly wish for, if faced with a real asteroid threat," Binzel told Insider.
However, scientists have yet to identify most of the hazardous space rocks that pass near our planet, which makes it unlikely we'd realise an impending danger five or ten years in advance. By mandating that NASA locate and track 90% of all objects 140 meters or larger in 2005, Congress attempted to address this problem. At that size, asteroids would obliterate a city as large as New York. Yet only 40% of these objects have been discovered by NASA.
"What that means is, for now, we are relying on luck to keep us safe from major asteroid impacts," Binzel said. "But luck is not a plan."
To Stop The Rock, We Must Understand The Rock
A city (hopefully an unimportant one like Brisbane) about to get proper warm...
Scientists participating in NASA's recent simulation had no idea how large it would be until a week before the asteroid was to hit Earth
"We didn't know if the object was 35 meters across or 500 meters across. And that makes a very big difference," said Planetary Science Institute researcher Sarah Sonnett.
The explosion of a 35-meter asteroid in the atmosphere could send shockwaves through the neighborhood. An asteroid 500 meters wide could decimate a city, covering an area the size of France.
Therefore, understanding the rock in as much detail as possible is an important part of stopping an asteroid from hitting the Earth. This includes its size, its path around the sun, and its composition. Scientists can then evaluate strategies to dismantle or disrupt the rock based on that information.
"It takes time to know thy enemy," Binzel said.
Scientists would like to study a hazardous asteroid as it passes Earth on its orbit around the sun a few times before it collides with Earth. Many years or even decades may pass before we are able to observe an asteroid more than once.
Part 2: Destruction or deflection?
A robo-fella having a biff with an interstellar boulder. Most likely this didn't happen.
NASA's planetary-defense arsenal consists of three main tools. An asteroid can be broken up into smaller, less dangerous chunks by detonating an explosive device near it. The second method is to fire lasers that can heat up and vaporize the space rock enough to alter its orbit. As a third option, a spacecraft could crash into the asteroid, knocking it off course.
That last strategy is about to be tested by NASA. Through its Double Asteroid Redirection Test in the fall of 2022, the space agency will send a probe directly at the asteroid Dimorphos.
All three options, however, would take years, Chodas said.
"Typically, that's a drawn-out, multi-year process to go from proposal to actually having a spacecraft on a launch vehicle – let alone the fact that you still have to cruise to get to your destination and deflect the asteroid," he said.
The asteroid would have to pass around the sun for one or two years before its trajectory actually changed enough to carry it away from Earth. The earlier scientists identify a hazardous space rock, the less expensive and ambitious a deflection mission would have to be.
Unless the asteroid is detected, all these methods are worthless.
"I think the best investment is in knowledge. The best investment is knowing what's out there," Binzel said. Completing such a list means identifying all near-Earth objects that could damage the Earth.
Asteroids will be tracked by a space telescope
This is the Spitzer Space Telescope in Earth orbit. It literally has nothing to do with this mission but we had to chuck something here.
NASA plans to track asteroids too dim for telescopes on Earth to see. In 2026, an infrared telescope would be launched into Earth's orbit, as part of the NEO Surveyor Mission (NEO stands for near-Earth object). On that mission team is Sonnet.
"If we do the job now of finding those objects and tracking them, knowing their orbits, knowing where they're going to head, and then characterizing their sizes, then we should be in really good shape," she said.
In theory, if the telescope works as planned, it should enable NASA to meet its Congressional mandate to find 90 percent of near-Earth objects.
As Binzel put it, the NEO Surveyor has been in "NASA mission limbo hell" for five years. Insufficient funding has prevented it from moving beyond the early development phase.
Sonnett is crossing her fingers that the upcoming review will be a success for the NEO Surveyor Mission. The mission will be assessed by NASA by the end of this month to see if it is ready to move forward. If it gets the green light, the team could begin developing prototypes, hardware, and software. Otherwise, the launch of the telescope could be further delayed.
"Because we now have the capability to detect and know what is out there, I think scientifically we have a moral responsibility to obtain that information," Binzel said. "It would be unconscionable that we were caught by surprise, by an asteroid impact that we could have seen coming."
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