An asteroid some 600 meters across swooped to within a few hundred thousand kilometers of Earth on Halloween, and the collective public reaction registered as barely more than a snigger. Various news stories called the rock “spooky” or the “The Great Pumpkin,” dismissing it as yet another near miss while we celebrated the holiday with costumes and candy. The sobering reality is that, only three weeks before its closest approach, Earth-based observers discovered a rock that could have wiped out life on a continent.

We view ourselves as a modern civilization, with dazzling rocket launches and pocket computers that allow us to communicate with anyone, anywhere in the world. Yet when it comes to detecting and deflecting asteroids, we are little better than our ancestors who evolved in Africa some 200,000 years ago. We can look up into the sky, see the bright fireball, and if we’re close enough to the impact, we will die. Just like them, except we might be able to tweet about the end of the world.

Unlike our ancestors, however, we actually have the technology to prevent such a calamity. For about $1 billion we could build an infrared space telescope to find all of the asteroids that threaten Earth, and we could then fly a mission to demonstrate our capacity to deflect one. NASA, in fact, could fund such efforts with about one percent of its annual budget over the next five years. The price of planetary insurance, it turns out, isn’t all that high.

But NASA and the general public have higher priorities, concedes Apollo 9 astronaut Rusty Schweickart. “The fact of the matter is, survival, which one would think would have the highest priority in the public interest, is not even on the priority list, let alone at the bottom of it,” he said. “That’s an interesting philosophical matter when you stop and think about it.”

No telescope

Late last year when I met with Schweickart and another astronaut, Ed Lu, they were both hungry for dinner. They had come to Houston to speak that evening about the asteroid threat to a gathering of alumni from the Massachusetts Institute of Technology, of which Schweickart was an alum. They also planned to visit the Johnson Space Center the next morning for an annual physical, part of a longitudinal study of astronauts.

They had to fast before the physical, and this was their last chance. “Do you mind if we eat while we talk?” Lu asked, before diving into a chicken Caesar salad.

Lu and Schweickart were among the founders of the B612 Foundation more than 14 years ago. The simple goal was to protect Earth from asteroid impacts. No one had previously taken ownership of the problem, Lu said. It wasn’t NASA’s responsibility to stave off danger, so NASA hadn’t focused its efforts on asteroids before.

Initially the group’s advocacy had some effect—in 2005 Congress passed a law requiring NASA, by the year 2020, to identify 90 percent of asteroids that were 140 meters or larger that potentially threaten Earth. But the Bush administration never asked for funding to carry out this mandate, so NASA never got it. At the time, the agency’s administrator, Michael Griffin, was instead scraping together every spare dollar he could find in NASA’s budget to pay for rockets and spacecraft that were part of the Constellation Program. That program was canceled in 2010 after more than $9 billion had been spent. Meanwhile, NASA has only found about 10 percent of the asteroids it was supposed to.

Frustrated by this, in 2012 the B612 Foundation announced plans to build its own space telescope, Sentinel, to search for asteroids that might threaten Earth. It would cost about $450 million. But fundraising efforts lagged. It turns out that’s a lot of money to raise for an existential threat. Late in 2015, NASA pulled the plug on a “Space Act Agreement” with the foundation that would have allowed the space telescope to use the agency’s deep space network to communicate with Earth. NASA said the foundation had failed to meet key milestones.

I met with Lu and Schweickart shortly after this NASA decision, expecting them to be pretty glum about the loss of NASA support for Sentinel. But that wasn’t the case. They seemed more or less pleased with progress that has been made in the field. While Sentinel may be stuck in neutral, other efforts have moved forward and seem likely to bear fruit in the coming decade.

Never tell me the odds

In reality, unless we’re really unlucky, no human alive today has to worry about asteroids. More than likely humanity can afford to wait another 10 or even 10,000 years to fully address the issue. In all of recorded history, in fact, there has yet to be a human death credibly attributed to an asteroid strike. Major asteroid impacts are the classic very low probability, very high consequence event.

Space debris hits Earth every day. Dozens of tons of tiny dust and rock chips traverse the upper atmosphere at speeds 10 to 100 times a rifle bullet. As these meteoroids encounter the atmosphere they heat up, glowing brightly, before vaporizing. It is the bigger objects we worry about, of course. The most famous meteoroid in modern history is the Tunguska event, which dissipated an estimated 10 megatons of TNT after bursting about 5 km above the Earth. Were this to strike a populated area today, it would likely devastate a large metropolitan area.

Such events occur every few hundred years, scientists estimate. Of greater concern are events caused by 100-meter or larger asteroids, equivalent to 100 megatons. This could cause total destruction on a national scale. The frequency of these is believed to be about one every 10,000 years. Put another way, there’s a one percent chance of such a strike occurring in the next century.

NASA

NASA

Virgil L. Sharpton

NASA

NASA

NASA

USGS



Carlos Roberto de Souza Filho

ImpactCraters.us

Carlos Roberto de Souza Filho

That’s not zero, and it’s also far from the worst case scenario. The Chicxulub impactor, an approximately 10km asteroid, struck Mexico about 65 million years ago. Such an event would wipe out human civilization, and indeed Chicxulub has been implicated in the worldwide extinction of non-avian dinosaurs.

The energy that asteroid gave off is incredible to think about. It’s estimated that Mount Pinatubo in the Philippines, which produced the second largest volcanic eruption of the 20th century in 1991, kicked up about 5 cubic kilometers of rock and debris into the atmosphere on suborbital trajectories.

By contrast the Chicxulub crater measures more than 100km across and is about 20km deep on average. This would have blasted about 500,000 cubic km of rock into the atmosphere. Millions of rocks would have then reentered the Earth’s atmosphere, making the skies incandescent and bringing surface temperatures to a boil. It’s estimated that 1 meter of the world’s oceans boiled off after the impact. “Imagine the thermodynamics of that,” Schweickart said.

This is unlikely to happen today, or tomorrow, or even during this millennium. The real question is how long a supposedly rational species plays dice with fate.