We made it! Osiris-Rex at Bennu

After over two years in transit through space, the NASA OSIRIS-REx spacecraft has reached target asteroid Bennu! The asteroid is about 500 meters in diameter and very rocky! It’s actually quite literally a pile of rocks and boulders loosely held together by gravity. In spaaaaaaaaaaaace

One of the primary objectives of the mission is to eventually swoop down and grab some samples.

Finding a sampling site will be challenging because we really want to find smaller particles that are easier to grab. It also helps to not crash the spacecraft into a truck-sized boulder while you’re at it. We think that some of the small depressions like this could contain fine particles for prospecting.

This is probably an impact crater. From here, it appears to be filled with finer materials and fewer big rocks.

We’re already seeing a lot of other cool stuff.

This appears to be an exposure of what geologists call bedrock. We’re probably just seeing the tip of the iceberg poking up here. In fact, the density of Bennu seems to be extremely low - 1200 kg/m3 compared to normal rock which is closer to 3000 kg/m3. This suggests that there might be some big voids and caves below the surface.

This interesting pile of rocks, currently informally dubbed the funeral pyre, might have once been a single rock that was broken apart over time by thermal fatigue and weathering. The surface of Bennu changes by about 100 Celsius every 4-hour day!

Aside from the sexy images, we also are collecting spectroscopic data to tell us about the composition of the minerals on the surface.

We’re already seeing strong spectroscopic signatures of hydrated (clay) minerals, much like some meteorites that we’ve recovered on Earth. This is fantastic news, because this is one of the main reasons that we chose this asteroid for this mission. Hydrated minerals usually formed by interaction with water and are usually closely associated with organic molecules. In short, asteroids like this one could have seeded the primordial Earth with the organic compounds that eventually led to life!

OSIRIS-REx is a big but meaningful acronym which describes the objectives of the mission. Although I haven’t discussed all of these things here, we so far have found ways to study everything in the name. Hang this on your fridge, Mom will be proud and maybe dad will stop beating you with jumper cables.

This mission is just getting started. One of prime objectives is to collect samples and return them to earth. Over the next year, we’re going to be studying the surface in detail and likely making tons of interesting scientific discoveries along the way. I’ll do my best to keep you tuned!

The universe tax