Opinion: Asteroid Bennu won't kill us all and of course NASA can stop it

OPINION: If you've been on social media in the past this week, you've probably seen headlines warning a killer asteroid is on its way to Earth, and there's nothing we can do.

"Doomsday asteroid taller than the Empire State building cannot be stopped by NASA," the New Zealand Herald's headline blared.

"Doomsday asteroid taller than the Empire State building that could WIPE OUT life on Earth in 2135 cannot be stopped by NASA, scientists warn," screamed the Daily Mail, slightly more verbosely.

"NASA can't save us from future apocalyptic asteroid," read the succinct headline on the New York Post.

Bennu fake news
None of this is true, not even the words in capital letters. Photo credit: New York Post/Daily Mail/New Zealand Herald

Odd, because none of this is true. To borrow a phrase from Donald Trump, it's fake news.

Yes, there is an asteroid that could hit Earth in the future. Yes, it's called Bennu. And yes, NASA is worried.

But unless you've gone to the source, read the original reporting or opened an academic journal, virtually nothing else you've likely read in the past week is true. Here's what is.

OSIRIS-REx

In 2016, NASA launched a probe called OSIRIS-REx towards an asteroid called Bennu. It's expected to reach the rock in August this year, where it will spend about a year-and-a-half taking measurements, before getting in close and scooping up a sample. The probe will return to Earth in the year 2023.

Bennu

Bennu is about 492m across, and orbits the Sun in the same region as Earth and Mars. It's estimated to have a one-in-2700 chance of hitting the Earth sometime in the 22nd century.

It's one of around 20,000 near-Earth objects that space agencies are keeping an eye on.  About 1400 of those are considered potentially hazardous to Earth.

If spherical, Bennu would have a total size of about 62 million cubic metres. The asteroid that killed most of the dinosaurs (those that didn't go on to become birds) was about 10km across - or 8400 times larger. The fact we're here discussing Bennu proves not even an asteroid thousands of times larger could wipe out life.

If Bennu hits, scientists have estimated it would have the power of 23 hydrogen bombs. But the effects would be largely localised.

"We're not talking about an asteroid that could destroy the Earth," OSIRIS-REx principal investigator Dante Lauretta said prior to the probe's launch. "We're not anywhere near that kind of energy for an impact."

His analysis determined whilst it certainly would be doomsday for those within 50km of the impact site, a few hundred kilometres away people would only notice an earthquake "similar to that of a passing truck", and there might be some loud wind and dust.

Bennu's orbit.
Bennu's orbit. Photo credit: NASA

Sure, millions could die if it hit exactly the right spot, but only 3 percent of the Earth's surface is urban.

"It may be destined to cause immense suffering and death," said Prof Lauretta.

If it hit the ocean (70 percent of the surface), there would be a tsunami like those that hit the Indian Ocean in 2004 or Japan after the Tohuku quake - bad news for those on the coasts, but life would go on for everyone else.

HAMMER

NASA is planning a new anti-asteroid defence system called HAMMER, which would use heavy spacecraft to either deflect or destroy incoming asteroids. The current plan is the craft will either ram asteroids at great speed or hit them hard with nuclear weapons.

Much of the reporting said NASA made an admission it could not stop Bennu, but this is wrong. While an accompanying study concluded using a "single HAMMER spacecraft as a battering ram would prove inadequate for deflecting an object like Bennu", most reports failed to mention HAMMER ships are also likely to carry nuclear weapons.

Bennu's numbers punched into the Impact Earth calculator.
Bennu's numbers punched into the Impact Earth calculator. Photo credit: Impact Earth/Purdue University/Imperial College London

Existing nukes would be strong enough to deflect Bennu, physicist David Dearborn told Buzzfeed News, one of the few outlets which reported the story accurately (with the no-less wonderful headline, 'Government scientists have a plan for blowing up asteroids with a nuke').

Also, Bennu's exact course is difficult to predict, so it may be that by the mid-22nd century a small nudge from a HAMMER is enough. We may have stronger, better weapons. Perhaps even ships capable of hitting asteroids at speeds we couldn't even imagine nowadays.

The Enterprise-D pictured firing photo torpedoes and phasers in the 24th century.
The Enterprise-D pictured firing photo torpedoes and phasers in the 24th century. Photo credit: Paramount/

And of all the hazards in space, Bennu isn't even the ranked the most likely to hit Earth. That honour belongs to (410777) 2009 FD, a binary asteroid with a one-in-1400 chance of meeting us in 2185.

But no one's going to click on a headline with the phrase '(410777) 2009 FD' in it, are they?

Dan Satherley is a senior digital news producer at Newshub.

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