What can be done?
To protect the planet from cosmic dangers, early detection is key. At the 2021 Planetary Defense Conference, scientists recommended a minimum of five to 10 years’ preparation time to mount a successful defense against hazardous asteroids.
If astronomers find a dangerous object, there are four ways to mitigate a disaster. The first involves regional first-aid and evacuation measures. A second approach would involve sending a spacecraft to fly near a small- or medium-sized asteroid; the gravity of the craft would slowly change the object’s orbit. To change a bigger asteroid’s path, we can either crash something into it at high speeds or detonate a nuclear warhead nearby.
These may seem like far-fetched ideas, but in November 2021, NASA launched the world’s first full-scale planetary defense mission as a proof of concept: the Double Asteroid Redirection Test, or DART. The large asteroid Didymos and its small moon currently pose no threat to Earth. In September 2022, NASA plans to change the asteroid’s orbit by crashing a 1,340-pound (610 kg) probe into Didymos’ moon at a speed of approximately 14,000 mph (22,500 kph).
Learning more about what threatening asteroids are made of is also important, as their composition may affect how successful we are at deflecting them. The asteroid Bennu is 1,620 feet (490 meters) in diameter. Its orbit will bring it dangerously close to Earth on Sept. 24, 2182, and there is a 1 in 2,700 chance of a collision. An asteroid of this size could wipe out an entire continent, so to learn more about Bennu, NASA launched the OSIRIS-Rex probe in 2016. The spacecraft arrived at Bennu, took pictures, collected samples and is due to return to Earth in 2023.
Spending on planetary defense
In 2021, NASA’s planetary defense budget was $158 million. This is just 0.7% of NASA’s total budget and just 0.02% of the roughly $700 billion 2021 U.S. defense budget.
This budget supports a number of missions, including the NEO Surveyor at $83 million, DART at $324 million and Osiris Rex at around $1 billion over several years.
Is this the right amount to invest in monitoring the skies, given the fact that some 60% of all potentially dangerous asteroids remain undetected? This is an important question to ask when one considers the potential consequences.
Investing in planetary defense is akin to buying homeowners insurance. The likelihood of experiencing an event that destroys your house is very small, yet people buy insurance nonetheless.
If even a single object larger than 460 feet (140 meters) hits the planet, the devastation and loss of life would be extreme. A bigger impact could quite literally wipe out most species on Earth. Even if no such body is expected to hit Earth in the next 100 years, the chance is not zero. In this low likelihood versus high consequences scenario, investing in protecting the planet from dangerous cosmic objects may give humanity some peace of mind and could prevent a catastrophe.