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Defend Earth

CORE ENTERPRISE

Decrease the risk of Earth being hit by an asteroid or comet

We help observers find, track, and characterize near-Earth asteroids and comets
We support the development of asteroid mitigation technology
We collaborate with the professional community and decision-makers to develop international response strategies to defend Earth from an asteroid or comet threat

The Challenge

The Earth shares its solar system with billions of asteroids and comets. The vast majority orbit the Sun far from our planet. Those whose orbits approach our own are callednear-Earth objects. The vast majority are harmless and pose no threat.

However, most people are aware of the large near-Earth object that devastated the entire planet 65 million years ago. While rare,these kinds of impacts are still possible. In fact, NEOs of many different sizes can pose serious threats.

An impact on or over a densely populated city could cause millions of deaths, and an impact on water could cause massive flooding on coastlines. Any major impact would lead to widespread damage, injury, and death, and would create unparalleled humanitarian and refugee crises around the world.

The good news is: an asteroid or comet impact is a natural disaster we can actually prevent—if we try.

The effort to prevent asteroid or comet impacts is calledplanetary defense.

What We're Doing

Bill Nye at IAC 2022 Bill Nye, CEO of The Planetary Society, presents on the importance of planetary defense at the 2022 International Astronautical Congress in Paris, France.Image: IAF Astro

Education and Outreach

We help more people understand the reality of the danger and the importance of protecting the Earth from asteroids, and we help them share this knowledge with family and friends.

We share freearticles,podcasts,videos, and aquarterly magazine to inform and engage the public on topics including planetary defense.
We host public events such asPlanetary Radio Live to share information in an entertaining way.
Wecreate resources to equip our members to teach others in their community about planetary defense.
We identify outreach opportunities for space agencies and the scientific community, such as the2029 asteroid Apophis flyby that is likely to spark a great deal of public interest.
We provide an online course to learn the basics of planetary defense.

Members attend the 2019 Day of Action Planetary Society members listen to a presentation during our annual Day of Action in Washington, D.C.Image: Antonio Peronace for The Planetary Society

Policy and Advocacy

We help more people communicate with their representatives in government about the preventable asteroid threat, and we help keep policymakers informed of the current state of planetary defense.

Our annualDay of Action brings Planetary Society members to Washington, D.C. to meet with their government representatives to advocate for planetary defense funding.
Our policy experts meet in person with policymakers to keep them informed of planetary defense issues.
We engage our members in planetary defense advocacy viapetitions and letters to Congress.
We provideguidance to the space agencies and the scientific community on planetary defense policies.
We equip members from around the world with the information they need to advocate locally for planetary defense measures.

Shoemaker NEO Grant recipients Amateur astronomers from the Associazione Romana Astrofili in Italy were able to improve their observations thanks to a Planetary Society Shoemaker NEO grant received in 2021.Image: Fabio Anzellini

Science and Technology

We directly support research and development projects for planetary defense through crowdfunding. Our members and supporters contribute directly to efforts to find, track, characterize, and deflect near-Earth objects.

The Planetary Society'sShoemaker NEO Grant Program provides grants, mostly to amateur astronomers, to assist with observations critical to finding and understanding Near-Earth Objects. Past Shoemaker grant winners have made tremendous contributions to discovery, tracking, and characterization of potentially dangerous near-Earth asteroids using the upgrades facilitated by the grants.
We support research on the impact history of Earth, funding the discovery and characterization of impact craters.
We provideseed funding for the development of new deflection technologies.

Some of the attendees at the 2015 Planetary Defense Conference in Frascati, Italy

ATTENDEES AT THE 2015 PLANETARY DEFENSE CONFERENCE IN FRASCATI, ITALYImage: ESA CC BY-SA IGO 3.0

Global Collaboration

We bring planetary defense experts together from around the world to work on advancing solutions to the asteroid threat.

Weco-sponsor, attend, and organize activities at academic conferences, including the biennial international Planetary Defense Conference. This is the only conference that brings together asteroid impact experts from all over the world to share updates, coordinate research, and engage the public.
We are official partners for the annualInternational Asteroid Day, which supports outreach events in communities around the world and online.

Defending Earth The Planetary Society's 5-step plan for tackling the asteroid threat.Image: The Planetary Society / Kim Orr

Latest Articles on Planetary Defense

Calendar of space events 2026

Space missions, rocket launches, and celestial events are coming our way in 2026.

When space rocks get too close for comfort

Some of the best-documented encounters Earthlings have had with asteroids and meteorites.

Impact on an Ancient earth, by Don Davis

How astronomers rank dangerous asteroids (and what that means for you)

A breakdown of the Torino scale, designed to give a quick sense of how worried you should be about an asteroid or comet.

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Educational Resources

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How to stop an asteroid from hitting Earth If we work together and properly utilize our space programs, then we will be able to prevent an asteroid impact when the time comes.

Artist's concept of near-Earth asteroids

Will an asteroid hit Earth? Your questions answered.

The Planetary Society presents a list of Frequent Asteroid Questions (FAQs).

Meet the Planetary Society’s Newest Asteroid Hunters

We talk with two of our 2019 Shoemaker NEO Grant winners, who received funding to help find, track, and characterize potentially hazardous asteroids.

Asteroids, Comets, and Other Worlds Pictures

Pretty pictures of asteroids, comets, and other small worlds.

The Biggest Little Asteroid Observatory

The Center for Solar System Studies, a perennial Planetary Society Shoemaker NEO Grant winner, is a small observatory that makes big contributions to near-Earth asteroid research.

Become A Member

When you become a member, you join our mission to increase discoveries in our Solar System and beyond, elevate the search for life outside our planet, and decrease the risk of Earth being hit by an asteroid.

Your role in space exploration starts now.