Preventing Our Extinction From Extraterrestrial Impacts Is Now Possible

Humanity finally has the proven technology, not so long ago limited to science fiction movies, to defend Earth from asteroids and comets on collision courses with us. 

We know from archaeology and astrophysics that this could lead to the extinction of our species, like the extraterrestrial impact in the Gulf of Mexico that killed the dinosaurs about 60 million years ago, or still devastating disasters that fall short of that worst case scenario, like the Younger Dryas climate event about fourteen thousand years ago (which was probably caused by an extraterrestrial impact somewhere in what is now Canada), that ended the Clovis culture of North America, led to widespread megafauna extinctions in the Americas, and postponed the Neolithic revolution globally by several thousands years.

This technology can defend us from genuinely existential threats to our species, and to life on Earth more generally.

While no known asteroid poses a threat to Earth for at least the next century, the catalog of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation. 

Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid. A test of kinetic impact technology was identified as the highest priority space mission related to asteroid mitigation. NASA's Double Asteroid Redirection Test (DART) mission is the first full-scale test of kinetic impact technology. The mission's target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by DART's impact. 

While past missions have utilized impactors to investigate the properties of small bodies those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft's autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in Dimorphos's orbit demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary.

R. Terik Daly, et al., "Successful Kinetic Impact into an Asteroid for Planetary Defense" arXiv:2303.02248 (March 3, 2023) (Accepted by Nature).

The other part of planetary defense is locating threats in time to do something about them now that we are capable of taking action. 

Telescope research programs like the Legacy Survey of Space and Time (LSST) which will begin in the year 2025, are dramatically improving our database of small solar system objects that can hep us better identify objects that could be existential threats to Earth and require active intervention: 

This multi-band wide-field synoptic survey will transform our view of the solar system, with the discovery and monitoring of over 5 million small bodies. The final survey strategy chosen for LSST has direct implications on the discoverability and characterization of solar system minor planets and passing interstellar objects.

And, when an object and its trajectory are discovered once, our understanding of gravitational dynamics at the solar system scale, and our computational capacity to apply on this knowledge of the relevant laws of physics to calculate the trajectories of these objections, means that we can know almost exactly where that object will be at every moment in time for thousands of years to come.

Another effort to identify solar system objects is using that reality to mine old data in order to leverage the information we already have about these objects.

We haven't yet marshaled the resources to put a full fledge planetary defense system with the capacity to identify all potential threats and neutralize them in place yet, however. And, doing so is pointless if we can't prevent ourself from causing our own extinction with the other main existential threats to the survival of our species in the form of pollution, weapons of mass destruction, and more speculatively, catastrophic missteps in developing biotechnologies or an artificial intelligence singularity.

But, planetary defense shouldn't be controversial, aside from the not small price tag required to address this "Black Swan" risk to humanity's survival. 

Not investing in planetary defense is the species level equivalent of cancelling your health insurance to save money - a pennywise, but pound foolish choice unless you are so poor that you have no other options. 

But, in a classic tragedy of the commons problem, the world's lack of fiscally strong global governmental institutions makes it hard to finance. So far, we are just relying on wealthy nations to foot 100% of the bill to develop it, even though it benefits everyone (even non-human animals and plants) on Earth.

Previous analysis of Planetary Defense issues can be found in this post at this blog.