A privately funded space telescope would scan the solar system for rocks that could cause the next mass extinction event on Earth.
NASA is busy whittling down a list of asteroids, looking for the best candidate for a mid-2020s rendezvous.
In plans announced last week, the agency says its Asteroid Redirect Mission will use an unmanned craft’s robotic arms to pluck a boulder off the selected space rock. It will then attempt to launch that boulder into orbit around the moon, where astronauts would later reconnect with it and obtain samples.
The controversial $1.25 billion project allows NASA to test an advanced Solar Electric Propulsion system, the type of capability necessary for a future trip to Mars.
The mission also has a secondary goal: saving Earth from possible catastrophe.
“Before the piece of the asteroid is moved to lunar orbit, NASA will use the opportunity to test planetary defense techniques to help mitigate potential asteroid impact threats in the future,” according to a press release.
After picking up the boulder, the spacecraft will spend several months hovering just above the asteroid, using gravitational interaction to try to nudge it just slightly off its orbit.
It’s a skill we should have down pat, because while this asteroid won’t be on a collision with Earth, others are.
The Day The Sky Exploded
“1908, June the 30th, there was a massive explosion over Siberia, over the area of the Tunguska River,” explains Dr. Paul Chodas, who manages the Near Earth Object program office at NASA’s Jet Propulsion Laboratory. “And we know now that it was likely a small asteroid that entered the atmosphere, and completely disintegrated.”
Eyewitnesses described a sky split in two, the clouds spewing flames, before a hot wind toppled 80 million trees. Many in Russia panicked at the sound, and headed for religious shrines.
The asteroid explosion was 1,000 times stronger than the atomic bomb dropped on Hiroshima.
“Fortunately, it was an uninhabited area, so there weren’t fatalities that we know of,” says Chodas.”
In 2013, another glimpse of asteroid power touched the city of Chelyabinsk, Russia.
“Maybe they are unlucky, or maybe it is because Russia is so enormous, so statistically speaking they are more likely to get hit. In this case, it was a much smaller rock,” says Jose Luis Galache, an astronomer at the Minor Planet Center in Cambridge, Massachusetts.
While Tunguska measured roughy 40 meters in size, according to Galache, the asteroid that exploded over Chelyabinsk was closer to 17 meters.
“But even so, it still caused some walls to collapse, broke a lot of glass,” and injured nearly 1,500 people.
Since 1947, the Minor Planet Center has been cataloging asteroids, keeping track of more than 675,000 of them.
“So if a new asteroid is discovered that is on a collision course with Earth, we are the first people to know about that.”
But they didn’t have the Chelyabinsk asteroid on their radar. No one did.
The Minor Planet Center does however keep an eye on other “potentially hazardous asteroids” and updates a list on its website.
“I haven’t actually checked today, but we are closing in on 1,400, I believe. And they are called potentially hazardous, and people tend to concentrate on the hazardous part, but I’d liked to stress they are potentially hazardous,” he says.
Assuming these asteroids follow their predicted orbits, they will remain a safe distance from Earth. But if one were to somehow speed up or slow down or otherwise get elbowed off its track…that’s the hazard.
Galache shrugs off the risk.
“As has been said, it is the only natural disaster that we can actually do something about. Because we can’t stop hurricanes or tornadoes or earthquakes, but if we discover an asteroid that is on a collision course, there are many options, and we can probably stop them.
“Of course, we have to find them first.”
A Dedicated Lookout
NASA spends $40 million a year searching for asteroids. Its focus has been tagging very large ones (more than 1 kilometer in diameter), of which the agency says its identified 96% of what’s believed to be out there. None pose a risk to Earth, at least over the next 100 years.
Smaller and medium sized asteroids are a different story, in part because they are so hard to see.
“If you’ve ever seen a meteorite, which is a piece of an asteroid that’s fallen on Earth, you’ll know that they are dark colored. They are almost the color of charcoal. So in space, you are looking for dark objects against a black background,” says astronaut Ed Lu, who flew three missions to the International Space Station.
“And that’s why we haven’t found a great majority yet of these asteroids. We don’t know where the great majority of them are, or where they are headed, or whether or not any of them is going to hit the Earth, or when.”
Lu now directs the B612 Foundation, which is attempting to launch its own privately funded detection system, called the Sentinel Space Telescope. Using infrared technology to map the inner-solar system, it could find as many as a half-million currently undetected asteroids.
With enough lead time, any of those that pose a risk could be moved off target with what Lu calls “fairly simple technology.”
“Unlike in the movies, where they use nuclear weapons and oil drillers, you don’t need to change the velocity very much. That means it is something as simple as running a small spacecraft into the asteroid. That’s basically sufficient in the great majority of cases to prevent an impact, and that is something we know how to do.”
If the asteroid still has years left to travel before impact with Earth, changing its speed by just a fraction of a mile per hour would move it off course.
NASA’s Redirect Mission, and its planned use of gravitational interaction to shift an asteroid, is in a similar vein.
But NASA isn’t contributing money to the Sentinel Space Telescope project. It’s $450 million price tag is being raised completely from donations by citizens of the world who see the value in an expanded asteroid detection effort.
Which brings up an interesting question. Of all the things you could donate your money to–all the charities and hospitals and public radio stations—where does planetary defense fall on your priority list?
We should all know by now what will happen if we don’t spot these asteroids in time. We’ve had plenty of warning, but is that enough to cut a check?
“The popular consciousness is aware that an asteroid killed off the dinosaurs, and that asteroids have hit the earth, and have destroyed a lot of things on this planet, repeatedly,” says Lu.
That doomsday scenario has been reinforced and re-imagined in books and movies like Armageddon and Deep Impact.
And maybe its Hollywood’s preference for exaggeration or pseudo-science or overly sappy endings that keep us from acting with more urgency. Maybe we’ve grown numb to the risk, or maybe its just that nobody wants to be chicken little.
“When you hear things like that, it is usually from people who basically have never looked at the odds,” says Lu. “Because the real question is, ‘Should somebody somewhere on this planet be trying to solve this problem?’ My answer to that is ‘Yes.’ And I’m just one of those people.”