Seeing this close-up photo of the asteroid Ryugu really makes you appreciate the Earth. Just look at it. A beat-up pile of rocks and dust blasted mercilessly by the solar wind and cosmic rays 100 million miles from the sun. Gasp! No atmosphere either. The kilometer-wide asteroid currently has a visitor, the Japanese Hayabusa-2 spacecraft. It orbits about Ryugu taking pictures while preparing to gather its first sample of dust and pebbly grit in late October.
Here’s what we know about Ryugu right now:
- It’s really dark! Ryugu reflects only 2% of the light it receives from the sun, absorbing the rest. Even the moon, which is as dark as an asphalt parking lot, reflects 12%.
- Its day is 7.63 hours long.
- It’s shaped like a top with an equatorial bulge.
- It’s covered with boulders, the largest of which — 426 feet (130 meters) across — sits atop the south pole.
- Its surface materials are all jumbled together in a diverse mineralogical mix.
- It has a mass of 450 million tons. Assuming it’s rock, it’s not very dense, which could mean it’s porous and potentially a “rubble pile” asteroid.
Originally, the spacecraft was to gather several samples from different areas to collect a diversity of materials. But it’s since been discovered that Ryugu is diverse-all-over. To reduce the risk involved in sampling, the folks at JAXA (Japan Aerospace Exploration Agency) may make just one attempt near the asteroid’s equator.
After a couple rehearsals in September and early October, the spacecraft will drop a reflective, weighted target marker on Ryugu’s surface to serve as an artificial landmark. The marker looks a little like a baby Sputnik with a reflective, gridded cloth exterior and short rods poking out. The spacecraft will shine a light on the marker, so the camera can fix on it. Then, as the probe gingerly descends to the asteroid’s surface, the landmark serves as a reference to detect any motion in the horizontal. If there is any the craft will fire thrusters to land with zero motion in the horizontal, ie. without skidding.
Hayabusa-2 determines its vertical distance and speed from the asteroid by aiming a laser at the surface in a procedure called laser ranging.
After the sample is retrieved, the craft departs to a safe location in orbit. The samples are stored in a return capsule that will be come roaring through the atmosphere and land in 2020.
In other asteroid news, NASA’s New Horizon spacecraft has made its first detection in a photo of its new flyby target, the asteroid Ultima Thule. Mission team members were thrilled – if not a little surprised – that New Horizons’ telescopic Long Range Reconnaissance Imager (LORRI) was able to see the small, dim object while still more than 100 million miles away, and against a dense background of stars. Taken Aug. 16 and transmitted home through NASA’s Deep Space Network over the following days, the set of 48 images marked the team’s first attempt to find Ultima with the spacecraft’s own cameras.
While it doesn’t look like much yet, finding its target early will help mission controllers refine the spacecraft’s course to the remote asteroid, a member of the Kuiper Belt beyond the orbit of Neptune. The photo is also the most distant image from the sun ever taken. At the time the images were taken, the New Horizons spacecraft was 4 billion miles (6.5 billion km) from the sun.
New Horizons will make its closest approach to Ultima Thule (only the coolest-named asteroid ever) at 12:33 a.m. EST on Jan. 1, 2019.