June 30 is Asteroid Day, and it seemed fitting to feature current and future asteroid missions.

Launched in 2014, Hayabusa2 arrived at the asteroid Ryugu in 2018. Once there, the spacecraft effectively shot a bullet, called an impactor, to expose undisturbed material just below the surface. Hayabusa2 collected a sample of this unweathered material to bring back to Earth. Because the sample was not subject to weathering from radiation and impacts with other rocks in space, it will give scientists a better idea of the asteroid’s properties. 

Hayabusa2 successfully returned those samples back to Earth in December 2020. That doesn’t mean its mission is over; the spacecraft will continue on and visit asteroid 2001 AV43 in 2029 and asteroid 1998 KY26 in 2031. These two asteroids are what are known as “fast rotators” because the time they take to spin on their axis is only ten minutes. Humanity has not visited an object like this before so it will provide a useful contrast to the rubble pile asteroids Ryugu and Bennu.

After arriving at the asteroid Bennu in December 2018, OSIRIS-REx spent several months imaging the surface in detail to find a suitable collection site. That turned out to be a challenge; the science team was expecting to find a smooth surface clear of major hazards. Instead, the images revealed huge boulders jutting out from an extremely rocky surface with very few smooth areas. 

With the help of over 3,500 volunteer citizen-scientists in CosmoQuest’s Bennu Mapper project who painstakingly marked over fourteen million rocks, boulders, and craters on thousands of images from OSIRIS-REx, spending about 45 minutes on each image, four sites were identified. Using this information to identify possible sample sites, OSIRIS-REx collected a sample in October 2020 from the sample site called Nightingale, located inside a crater near the asteroid’s north pole. The spacecraft began its return to Earth in mid-May 2021, and it will arrive in September 2023. After it delivers its sample to Earth it, too, will continue on to an extended mission.

Launching later this year is humanity’s revenge for an asteroid taking out the dinosaurs at the end of the Cretaceous Period. The Double Asteroid Redirection Test, or DART, is pretty much what it sounds like: a test to see if humanity can redirect not one but two asteroids.

The double asteroid target for this NASA mission is the binary asteroid system Didymos. A binary system is one where two objects orbit each other as they orbit the Sun. In this case, the system is the Didymos and its smaller companion Dimorphos [Ed. note: DIDYMOON!].

Before I continue, I want to point out that their orbit doesn’t cross Earth’s orbit, and there is absolutely no threat of either Didymos or Dimorphos hitting us. I repeat: they will not impact Earth.

With that said, the fact that it will never collide with our planet makes it the perfect test subject for this mission. DART will impact Didymos, and because of that not crossing paths with Earth bit, scientists and engineers will be able to safely see if humanity can change the orbit of a potentially hazardous asteroid.

And its companion Dimorphos? It’ll be fine. The kinetic energy resulting from the test isn’t high enough to disturb its orbit in a way that would result in a future collision.

More Information

Launch of “Hayabusa2” by H-IIA Launch Vehicle No. 26 (JAXA)

Arrival at Ryugu! (JAXA)

Shooting bullets into Ryugu! (JAXA)

Images of the capsule after landing back on Earth (JAXA)

Extended mission after Hayabusa2 returns to Earth (JAXA)

Asteroid Operations (OSIRIS-REx)

CosmoQuest Citizen Scientists Help Map Asteroid Bennu (PSI)

NASA’s OSIRIS-REx Spacecraft Heads for Earth with Asteroid Sample (OSIRIS-REx)

DART Mission Overview (JHUAPL)