How to defend the Earth from asteroids

How to defend the Earth from asteroids
A collection of images from the WISE spacecraft of the asteroid 2305 King, which is named after Martin Luther King Jr. The asteroid appears as a string of orange dots because this is a set of exposures that have been added together to show its motion across the sky. These infrared pictures have been color-coded so that we can perceive them with the human eye: 3.4 microns is represented as blue; 4.6 microns is green, 12 microns is yellow, and 22 microns is shown as red. From the WISE data, we can compute that the asteroid is about 12.7 kilometers in diameter, with a 22% reflectivity, indicating a likely stony composition. Credit: NASA

A mere 17-20 meters across, the Chelyabinsk meteor caused extensive ground damage and numerous injuries when it exploded on impact with Earth's atmosphere in February 2013.

To prevent another such impact, Amy Mainzer and colleagues use a simple yet ingenious way to spot these tiny near-Earth objects (NEOs) as they hurtle toward the planet. She is the principal investigator of NASA's asteroid hunting mission at the Jet Propulsion Laboratory in Pasadena, California, and will outline the work of NASA's Planetary Defense Coordination Office this week at the American Physical Society April Meeting in Denver—including her team's NEO recognition method and how it will aid the efforts to prevent future Earth impacts.

"If we find an object only a few days from impact, it greatly limits our choices, so in our search efforts we've focused on finding NEOs when they are further away from Earth, providing the maximum amount of time and opening up a wider range of mitigation possibilities," Mainzer said.

But it's a difficult task—like spotting a lump of coal in the night's sky, Mainzer explained. "NEOs are intrinsically faint because they are mostly really small and far away from us in space," she said. "Add to this the fact that some of them are as dark as printer toner, and trying to spot them against the black of space is very hard."

How to defend the Earth from asteroids
An image of the proposed Near-Earth Object Camera (NEOCam) mission, which is designed to find, track and characterize Earth-approaching asteroids and comets. Using a thermal infrared camera, the mission would measure the heat signatures of NEOs regardless of whether they are light or dark colored. The telescope's housing is painted black to efficiently radiate its own heat into space, and its sun shield allows it to observe close to the Sun where NEOs in the most Earth-like orbits spend much of their time. In the background is a set of images of main belt asteroids collected by the prototype mission NEOWISE; the asteroids appear as red dots against the background stars and galaxies. Credit: NASA

Instead of using to spot incoming objects, Mainzer's team at JPL/Caltech has leveraged a characteristic signature of NEOs—their heat. Asteroids and comets are warmed by the sun and so glow brightly at thermal wavelengths (infrared), making them easier to spot with the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) telescope.

"With the NEOWISE mission we can spot objects regardless of their surface color, and use it to measure their sizes and other surface properties," Mainzer said.

Discovering NEO surface properties provides Mainzer and her colleagues an insight into how big the objects are and what they are made of, both critical details in mounting a defensive strategy against an Earth-threatening NEO.

For instance, one defensive strategy is to physically "nudge" an NEO away from an Earth impact trajectory. But to calculate the energy required for that nudge, details of NEO mass, and therefore size and composition, are necessary.

How to defend the Earth from asteroids
The NEOWISE space telescope spotted Comet C/2013 US10 Catalina speeding by Earth on August 28, 2015. This comet swung in from the Oort Cloud, the shell of cold, frozen material that surrounds the Sun in the most distant part of the solar system far beyond the orbit of Neptune. NEOWISE captured the comet as it fizzed with activity caused by the Sun's heat. On November 15, 2015, the comet made its closest approach to the Sun, dipping inside the Earth's orbit; it is possible that this is the first time this ancient comet has ever been this close to the Sun. NEOWISE observed the comet in two heat-sensitive infrared wavelengths, 3.4 and 4.6 microns, which are color-coded as cyan and red in this image. NEOWISE detected this comet a number of times in 2014 and 2015; five of the exposures are shown here in a combined image depicting the comet's motion across the sky. The copious quantities of gas and dust spewed by the comet appear red in this image because they are very cold, much colder than the background stars. Credit: NASA

Astronomers also think that examining the composition of asteroids will help to understand how the solar system was formed.

"These objects are intrinsically interesting because some are thought to be as old as the original material that made up the solar system," Mainzer said. "One of the things that we have been finding is that NEOs are pretty diverse in composition."

Mainzer is now keen to leverage advances in camera technology to aid in the search for NEOs. "We are proposing to NASA a new telescope, the Near-Earth Object Camera (NEOCam), to do a much more comprehensive job of mapping asteroid locations and measuring their sizes," Mainzer said.

NASA is not the only space agency trying to understand NEOs. For instance, the Japan Aerospace Exploration Agency's (JAXA's) Hayabusa 2's mission plans to collect samples from an asteroid. And in her presentation Mainzer will explain how NASA works with the global space community in an international effort to defend the planet from NEO impact.

Explore further

Asteroid-hunting spacecraft delivers a second year of data

More information: The presentation, "NASA's Planetary Defense Coordination Office at NASA HQ," will take place on Tuesday, April 16, in room Governor's Square 14 of the Sheraton Denver Downtown Hotel. Abstract:
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Apr 16, 2019
How to defend the earth from people? the risk is higher than from asteroids

Apr 16, 2019
@ mqr, we have been wrecking earth for decades while offering band-aide solutions. There seems little to be done about it. At least I don't see anything being done about it. Quite the opposite actually.

However, we might be able to deflect an asteroid, comet, whatever. It is estimated that one of these of about 2 km in diameter or more (depending on relative impact speed and angle of impact) would be big enough to take us out. Perhaps that is the solution to the earth's problem. Take out the pest(s) which are causing so much trouble, so the rest of the critters can recover.

In any event, we better hope it is a NEO. A long period comet unknown to us would likely be too big of a surprise to give us time to do anything, except to bend over and kiss ourselves goodbye!

Apr 16, 2019
However, we might be able to deflect an asteroid, comet, whatever.
The deciding factor is that we have permission to defend against asteroids. Nobody makes any money from letting them come here, unlike the wealth generated from carbonizing the atmosphere. And as with nuclear war, everybody's assets are at risk from asteroids. So there's no Big Chicxulub lobby.

Apr 17, 2019
bunker busters

Apr 17, 2019
LOL. PhD in what, piling high and deep?

2Km sphere of water masses what, at interplanetary velocity has what momentum? How much momentum can humans lift far enough to make a difference? Heck, we can just barely get around the Moon.

Apr 17, 2019
@ddaye I got a quite a chuckle out of your notion that there is not a "Big Chicxulub lobby." Truth is, how can you be sure? Might be a stealth lobby of some kind. Think religion!

To be sure, not "everybody's assets are at risk from asteroids". It clearly depends on the size. So long as the asteroid is small enough (like that bolide at Tunguska), space rocks could be diverted to weaponry. Think of all the little rocks out there that small thrusters could be planted on to change their trajectory enough to decimate just about anything. A city, a country. So long as collateral damage is minimal, it works, and no radiation. Even neutron bombs are taken out of the equation. Perfecto!

Trick is finding the right rocks and clandestinely planting steering mechanisms on them. We are getting so good at space navigation you could probably take out Moscow with a small asteroid, with everyone thinking it was simply a natural event. Oh, and best to make sure the thinking stays that way.....

Apr 17, 2019
What's up doc?
Whatever you're smoking. STOP. It ain't worth the brain damage.

Apr 18, 2019
I fully support this line of research and action.

To the extent that the technology could be easily weaponized, I suspect the international community, as well as the limited number of superpowers capable of doing it, as well as the prospect for a "balance of power" extinction-level-event meteors in a "mutual assured destruction" would likely carry on the current nuclear tradition, albiet raising the stakes dramatically.

Apr 18, 2019
@JaxPavan, raising such weaponized rocks to extinction-level would not help anyone, and we already have those things with nukes. Using rocks for minimal stealth attacks is the only practical app, and that mainly as a threat. It is not outside the range of things countries could do to destroy another.

Look at Putin telling the world he has developed a nuclear powered torpedo with a huge warhead seeded with cobalt-60. This thing is supposed to have a yield of 100-200 megatons and is designed to create a massive tsunami spreading devastation and intense radioactive contamination along much of the U.S. east coast. Not a very friendly notion.

He apparently is not overly concerned about MAD, so maybe we should give him extra reasons to be. Weaponized space rocks are something only the U.S. and maybe the E.S.A. could actually come up with, so any stealth approach is unlikely. But punching Putin in his abs with the notion of a killer space rock heading to Moscow just feels right!

Apr 20, 2019

ELE is ultimate MAD. I could see any outclasses superpower going there for security, from Russia to China to Japan to the EU.

Nuclear MAD was always a bit of a myth, like nuclear winter was a myth. Nuclear MAD is really about destroying civil society, military bases, and much population, but WWIII would go on, and we would see a real draft again. . .

Apr 20, 2019
How to defend the earth from people? the risk is higher than from asteroids

The Earth is a rock. Rocks don't need defending, sentient beings do.

13 hours ago
@JaxPavan, that depends on the level of nuclear exchange. Clearly ELE from space is the ultimate, but there is every reason to believe that a significant nuclear exchange could wipe out humans. It is much more than just nuclear winter.

I believe you need to brush up on your studies on the nuclear weapons threat to human civilization (the threat ain't over til its over, and it ain't over) :


And I for one am happy that the generals and leaders did not believe MAD was/is a myth. To be certain, a myth is the last thing that it is.

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