When a dangerous asteroid threatens Earth, humanity will have to work together, NASA says

illustration of two asteroids in space, with earth in the background
An artist's illustration of asteroids headed toward Earth. (Image credit: ESA — P.Carril)

A threatening asteroid could bring Earth's oft-squabbling nations together, at least for a while.

Dealing with a big, dangerous asteroid that appears to have our planet in its crosshairs will require a healthy dose of international cooperation, experts say — and it's best to start thinking about that scenario now, while we have enough time to lay out a potential response framework.

The United Nations (UN) has developed "procedures for responding to tsunamis and other big events," Leviticus "L.A." Lewis, the U.S. Federal Emergency Management Agency (FEMA) detailee to NASA's Planetary Defense Coordination Office (PDCO), said during a press briefing on Thursday (June 20). "But for an asteroid impact, we're thinking the scale of it is going to be such that we actually do need to discuss at this time what it would take for an international response on such a large scale," he added.

Part of that response would involve coordinating evacuations of people in the potential impact zone, which would likely cover a large swath of ground, given how fast asteroids move through space and how difficult it is to nail down a newfound asteroid's trajectory. (Small uncertainties in that calculated path would result in big differences in the projected impact point on Earth. And newfound space rocks are the ones to worry about; none of the big asteroids we already know about pose a threat to our planet for the foreseeable future.)

"If we talk about multiple nations and people having to move around, and responding to a very large area, that could be a challenge," Lewis said. "We need to organize and start discussing what it would really take to coordinate a large effort. And who would be in charge? What organization? How would we set it up? Would it be the U.N.? Would it be a combination of international organizations? How would we actually accomplish that? So, that's the new challenge."

Lewis was discussing the results of the fifth Planetary Defense Interagency Tabletop Exercise, an asteroid-threat simulation that was held April 2 and April 3 at the Johns Hopkins Applied Physics Laboratory (APL) in Maryland. 

The exercise — the fifth of its kind that researchers have performed, following similar efforts in 2013, 2014, 2016 and 2022 — aimed "to inform and assess our ability as a nation to respond effectively to the threat of a potentially hazardous asteroid or comet," NASA officials said in a statement.

The participants — nearly 100 people from various U.S. federal agencies and international institutions — considered the following hypothetical scenario: Scientists just discovered a relatively large asteroid that appears to be on an Earth-impacting trajectory. There's a 72% chance it will hit our planet on July 12, 2038, along a lengthy corridor that includes major cities such as Dallas, Memphis, Madrid and Algiers.

But this is just an initial snapshot, with many key facts still fuzzy or unknown. For example, it's unclear how big the asteroid is; its estimated size range is 200 feet to 2,600 feet (60 to 800 meters). And researchers don't know its composition, which is a very important detail; a dense metallic or stony asteroid would behave quite differently — both during a potential deflection attempt and upon impact — than a "rubble pile" of dirt and gravel like Bennu, the space rock that NASA's OSIRIS-REx probe visited and sampled a few years ago.

"The uncertainties in these initial conditions for the exercise allowed participants to consider a particularly challenging set of circumstances," Lindley Johnson, planetary defense officer emeritus at NASA Headquarters in Washington, said in the same statement. "A large asteroid impact is potentially the only natural disaster humanity has the technology to predict years in advance and take action to prevent."

Related: Potentially dangerous asteroids (images)

Representatives from NASA, FEMA and the planetary defense community participate in the 5th Planetary Defense Interagency Tabletop Exercise in early April 2024. The goal was to inform and assess our ability as a nation to respond effectively to the threat of a potentially hazardous asteroid or comet. (Image credit: NASA/JHU-APL/Ed Whitman)

More knowledge about the newfound space rock won't be forthcoming for a while: The exercise stipulated that it just disappeared behind the sun from Earth's perspective, making further telescope observations impossible for the next seven months.

The participants in the April exercise — which was organized by the PDCO and FEMA, with help from the U.S. Department of State Office of Space Affairs — talked through the potential next steps.

They examined three main near-future possibilities, one of which was to do nothing until more telescope observations can be made. The other two were to start studying, and possibly even developing, a fact-finding mission to the threatening space rock — either a flyby or a more involved, purpose-built rendezvous effort, which would sidle up to the asteroid for a lengthy stretch.

The flyby would likely cost between $200 million and $400 million. The rendezvous mission's price tag would be steeper — in the neighborhood of $800 million to $1 billion.

Most of the exercise's senior leaders favored options two or three "but noted [that] political realities would limit immediate action," states an initial report about the simulation, which you can find here.

That report includes a selection of comments from anonymous exercise participants. "The most important item of the morning was the discussion involving the political nature of the decision making," one such comment read.

Another highlighted the global nature of the challenge, as Lewis did: "International involvement early will be critical. That credibility is essential and must be established now."

The exercise didn't result in any ironclad rules that must be followed when a threatening asteroid is discovered. (And planetary defense experts say this is indeed a matter of "when" rather than "if;" at some point, a big space rock will head our way.) But no such prescriptions were expected; rather, the main goal was to talk through the possibilities and gain more familiarity with the steps the scientific and international community would take to deal with an incoming asteroid.

"The actual plan, the specific exercise results, aren't really anything," Johnson said in Thursday's briefing. "It's the actual going through the process of doing the planning and working together, communicating and working with each other, that is the real purpose of this exercise."

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Mike Wall
Senior Space Writer

Michael Wall is a Senior Space Writer with Space.com and joined the team in 2010. He primarily covers exoplanets, spaceflight and military space, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.

  • Classical Motion
    NASA should know better. NASA needs to test and find several methods on it's own right now. Depending on future cooperation is foolish.

    We have plenty of targets and Mars as a pivot for it. Let's learn how to steer them now.
  • billslugg
    Yes, international cooperation is great but how is that going so far?
    If a space rock is headed towards the US, the US has the absolute right to deal with it unilaterally.
    The undertone of the article is that some sort of international group should have some level of decision making power. Like, for example, Russia could veto our proposed action in the Security Council. Thanks, but no thanks.
  • Unclear Engineer
    I think that this particular exercise sounds rather unrealistic, even for the not so distant future.

    The emphasis on the response on the ground seems out of place. We know that some people refuse to recognize reality and fight to the death over "principles", and can expect that even in any sort of impact prediction. Some won't believe it and won't move. Some will blame it on others and fight them. Some will not want others to come to their country from the projected impact areas and will stall the processes.

    But, what the more rational and inventive engineers and scientists do during all of that political running in circles screaming and shouting is what will determine the fate of us here on Earth. So, better for those people to be trying now to coordinate internationally about how to decide on the best defense tactics.

    Experiments such as DART need to be done now. Not just DART type, but other types of tactics need to be tested.

    Scientific visits and sampling of various types of space objects need to be done now. We need to share the findings internationally.

    Quick launch capabilities need to be arranged now. And Space Force and SpaceX are working on that now.

    And a billion dollars for a probe shouldn't be a problem with funding stuck in Congress. Musk could do that with pocket money - and probably would.

    To me, the real technical issues that can be resolved by research and planning are the ones we need to focus on now, not the politics. We don't want Russia launching a mission to blow-up the same thing that NASA is launching a mission to deflect by impact and China is launching mission to deflect by attaching a rocket motor. The conflicts could cause all three to fail, even if all of them would individually succeed. So, it is the technological response that we need to coordinate internationally.

    But, I agree with Bill that we also must have the ability to act alone. There is always the possibility that the projected impact would look like an opportunity for some group that is an adversary of the people in the impact area, and they could intentionally stall the U.N. or any other multinational decision making group.
  • Atlan0001
    To borrow from Edmund Burke, Winston Churchill, and 'complexity systems' scientists:

    When an evil, a threat to all, combines and comes to a point, it will be necessary for the disparate to temporarily associate for the good of all.
  • COLGeek
    I truly understand and appreciate the sentiment, but I'll not start holding by breath in anticipation just yet.

    Even with an impending catastrophic event, I don't see the level of international cooperation desired, I am sad to say.
  • zombie_reaper
    Destroying a large asteroid on a collision course with Earth is a significant challenge, but several methods have been proposed by scientists and space agencies. Here are some potential solutions:

    1. **Kinetic Impact**: This involves sending a spacecraft to collide with the asteroid at high speed to change its trajectory. NASA's DART (Double Asteroid Redirection Test) mission is an example of this approach.

    2. **Nuclear Explosives**: Detonating a nuclear device near or on the asteroid could potentially change its course by either blowing it apart or pushing it off course. This method is controversial due to the risks associated with nuclear explosions in space.

    3. **Gravity Tractor**: A spacecraft could fly alongside the asteroid for an extended period, using its gravitational pull to slowly alter the asteroid's trajectory. This method requires precise navigation and a long lead time.

    4. **Laser Ablation**: Focusing powerful lasers on the asteroid's surface could vaporize material and create a thrust that changes the asteroid's path. This approach requires advanced laser technology and significant power sources.

    5. **Solar Sails**: Attaching large reflective sails to the asteroid could use the pressure of sunlight to gradually alter its course. This method is slow but could be effective given enough time.

    Given the scenario in the image, where there's a 72% chance of impact on July 12, 2038, it's crucial to act quickly. The first step would be to conduct a detailed assessment of the asteroid's size, composition, and trajectory. Based on this data, an international effort involving space agencies and experts would determine the best approach.

    ### Proposed Plan:
    1. **Assessment and Monitoring**:
    - Deploy telescopes and space probes to gather precise data on the asteroid.
    - Continuously monitor its trajectory and make adjustments to the strategy as needed.

    2. **Kinetic Impact Mission**:
    - Design and launch a kinetic impactor mission to collide with the asteroid and alter its course.
    - This could be supported by secondary missions to gather data and ensure success.

    3. **Backup Plan**:
    - Prepare a secondary mission involving nuclear explosives as a last resort if the kinetic impactor fails.
    - Coordinate international efforts for rapid deployment.

    4. **Public Communication**:
    - Keep the global public informed about the asteroid and the steps being taken to mitigate the threat.
    - Ensure transparency to maintain public trust and cooperation.

    By combining these approaches with international cooperation and technological expertise, it would be possible to mitigate the threat posed by the asteroid and protect major cities such as Dallas, Memphis, Madrid, and Algiers from potential impact.
  • Unclear Engineer
    Fourteen years of warning time might be a very optimistic scenario. As we study the solar system in more detail, we will probably get a pretty good idea of what is in orbits inside Jupiter's orbit, and have long warning times of potential collision dates. So, the risk will probably be greatest for collisions with objects coming in from the Oort Cloud or interstellar space that would hit Earth on its first pass around/by the Sun. Worst case would be that the object is first at a detectable range when not in a detectable position, due to being on the other side of the Sun from the Earth. We might only have about a year's warning time before impact and less time to avoid an impact. So, that is what we really need to plan for. And, the laser ablation approach seems optimal for that scenario, so I think we should be putting some serious effort into developing and demonstrating it.
  • JamesK111
    1. America doesn't have to deflect the asteroid, we just need to slow it down enough for the USA to rotate out of the way. Once again Canada gets a free ride (Emo Phillips)
    2. It's absurd that practically zero dollars are spent on how to stop the phenomenon that we know wiped out 90% of life on Earth in the past, but want to spend trillions and further impoverish the world's poor trying to stop a potential for what is at most a manageable climate change over the next century.
  • JamesK111
    Unclear Engineer said:
    Not necessarily true. If it is going to hit a U.S. city, why would Russia or China spend the money to "save" us?

    That was "JamesK111" only post to Sapce.com. And, it really doesn't make any sense. So, why bother to engage in a conversation about it. We might be talking to a bot.
    1. It was a joke - apologies for the misfire.
    2. Not a bot. A real person who worked on Kepler, Phoenix, MER (Spirit & Opp. to the public), MSL (Curiosity), Cargo & Crew Dragon, M20 (Perseverence)

    I rarely comment on Space.com and couldn't remember my login.
  • Unclear Engineer
    I deleted my post when I saw the correction, but apparently the "notification" of my post had already been e-mailed.