June 30th is Asteroid Day!


The United Nations has designated June 30 as Asteroid Day to increase public awareness about the risks and opportunities of asteroids in our Solar System.


As most people are aware that asteroids mostly inhabit the Asteroid Belt which lies between Mars and Jupiter.  These large bodies of rock and ice are the "left-overs" that didn't coalesce into planets or moons when our solar system formed and many of them are older than Earth! As of June 29, 2021, 1,086,655 asteroids have been identified. In June alone, 164 new objects have so far been discovered. Finding asteroids is truly an international endeavor.


Finding asteroids is no easy task. Currently, there is an active and massive research program underway to identify as many asteroids as possible so that we can determine their orbits and characteristics. The need to find these objects became much more urgent once scientists realized that asteroids have often impacted Earth and the other planets throughout geologic time. Remember the dinosaurs?


Several spacecraft have visited asteroids over the years—mostly as fly-by missions on the way to other places. Four have actually landed on asteroids. The first landing was NASA’s Near Earth Asteroid Rendezvous (NEAR) spacecraft on the asteroid Eros in February, 2001. Japan has so far returned samples to Earth from two asteroids. The US has a load of asteroid samples on its way back to Earth right now.


Many asteroids have their orbits shifted or perturbed, by gravitational interaction with Mars and the giant planet Jupiter. A distressingly large number of asteroids have left the asteroid belt and now follow orbital paths that bring them across Earth’s own orbit. These asteroids are called Near Earth Objects or NEOs. The Minor Planet Center lists 26,126 of these NEOs currently known. 158 of these have been discovered in June, 2021 so far. This is potentially problematic. Sooner or later, Earth and one (or more) of these objects will cross paths. The good news is that none of the known asteroids will cross paths with Earth in the next 100 years.


Many scientists have developed plans for investigating how we might move one of these NEOs, should it be found to be on a collision course with Earth. The slightest push could be all it takes for an asteroid to miss Earth. All we need is a miss. Moving an asteroid is a challenging project. It has never before been attempted.


This winter, NASA and the Johns Hopkins University Applied Physics Laboratory will launch the Double Asteroid Redirection Test, or DART spacecraft to the asteroid Didymos. This asteroid is a double asteroid, having a small moon orbiting it. This tiny moon, Dimorphos, will be DART’s target. DART will deliberately crash directly into the smaller asteroid at 4.1 miles per second in October, 2022. It is expected to change this mini asteroid’s speed by a mere 0.4 millimeters per second. This isn’t much but it is humanity's first attempt to move an asteroid. In this way, we can incrementally build up our asteroid redirecting skills. Life on Earth might just end up depending on it.