Astronomers Are Getting Better at Detecting Asteroids Before They Hit Earth – and It Could Save Us from Catastrophe

It is made even more challenging by the fact that there are many more smaller objects out there than bigger ones. Some of these smaller objects are nevertheless of sufficient size to cause damage on Earth, so we still need to monitor them. They are also reasonable faint and therefore harder to see with telescopes.

It can be difficult to predict the paths of smaller objects long into the future. This is because they have gravitational interactions with all the other objects in the solar system. Even a small gravitational pull on a smaller object can, over time, alter its future orbit in unpredictable ways.

Funding is crucial in this effort to detect dangerous asteroids and predict their paths. In 2023, Nasa allocated US$90 million (£69 million) to hunt for near Earth objects (NEOs). There are several missions being developed to detect hazardous objects from space, for example the Sutter Ultra project and Nasa’s NEOsurveyor infrared telescope mission.

There are even space missions to explore realistic scenarios for altering the paths of asteroids such as the Dart mission. Dart crashed into an asteroid’s moon so that scientists could measure the changes in its path. It showed that it was indeed possible in principle to alter the course of an asteroid by crashing a spacecraft into it. But we’re still far from a concrete solution that could be used in the event of a large asteroid that was really threatening Earth.

Detection programs create a huge amount of image data every day, which is challenging for astronomers to work through quickly. However, AI could help: advanced algorithms could automate the process to a greater degree. Citizen science projects can also open up the task of sorting through the data to the public.

Our current efforts are working, as demonstrated by the detection of the relatively small asteroid RW1. It was only discovered briefly before it struck Earth, but gives us hope that we are on the right track.

Asteroids less than 25m in diameter generally burn up before they can cause any damage. But objects of 25-1,000 meters in diameter are large enough to get through our atmosphere and cause localized damage. The extent of this damage depends upon the properties of the object and the area where it will hit. But an asteroid of 140 meters in size could cause widespread destruction if it hit a city.

Luckily, collisions with asteroids in this size range are less frequent than for smaller objects. A 140 meter diameter object should hit Earth every 2,000 years.

As of 2023, statistical models suggest that we know of 38% of all existing near earth objects with a size of 140 meters or larger. With the new US Vera Rubin 8.5m telescope, we hope to increase this fraction to roughly 60% by 2025. Nasa’s NEOsurveyor infrared telescope could identify 76% of asteroids 140 meters in size or bigger by 2027.

Asteroids larger than 1 kilometer in size have the ability to cause damage on a global scale, similar to the one that helped to wipe out the dinosaurs. These asteroids are much rarer but easier to spot. Since 2011, we think we have detected 98% of these objects.

Less comforting is the fact that we have no current realistic proposal for diverting its path – though missions like Dart are a start. We might eventually be able to compile a near-complete list of all possible asteroids that could cause global impacts on Earth.

It’s much less likely that we will ever detect every object that could cause localized damage on Earth – such as destroying a city. We can only continue to monitor what’s out there, creating a warning system that will allow us to prepare and react.

Daniel Brown is Lecturer in Astronomy, Nottingham Trent University. This article is published courtesy of The Conversation.