Transcript for "Searching for Earth's Trojan Asteroids"


Hi, I'm Jim Green, the director of Planetary Science here at NASA.


OSIRIS-REx is an opportunity to go back in time and visit an asteroid called Bennu. Bennu is a very primitive object, created at the birth of our solar system. OSIRIS-REx is going to go there, orbit Bennu for more than a year, and bring back a sample.


Since September, when we launched OSIRIS-REx, it has made wonderful progress in the solar system, but is getting close to a very important place.


This is the Earth's Lagrangian point L4.


Now a Lagrangian point are special regions in and around our orbit, for which the gravitational interaction between the Earth and the sun nearly cancels out. This allows an object to be trapped and remain in that location.


So what's trapped at L4? Well we don't really know. We only know what's trapped at L4 around other planets. At Jupiter these are hundreds and hundreds of objects that we call Trojans. And so, at Earth's L4, if we find anything we'll be calling them Earth Trojans.


Now what are Trojans? Well, these are small bodies caught in this orbit for billions of years. The Earth has swept up all kinds of material to be created as we know it today, and what's left are those things that are sitting at L4.


That's what makes it really exciting to be able to go there, and OSIRIS-REx is nearly there. Beginning February 9th, OSIRIS-REx is going to turn on its scanning camera. It's going to scan the areas, it's going to look for these objects.


To follow along with OSIRIS-REx, please go to, or go to