26 ASTRONOMY • JANUARY 2020
In June 2018, the Japan Aerospace
Exploration Agency’s (JAXA) Hayabusa2
spacecraft began its exploration of the
near-Earth asteroid Ryugu. In October
2018, the spacecraft dropped its Mobile
Asteroid Surface Scout (or MASCOT)
lander to examine the asteroid up close.
Hayabusa2 itself was scheduled to swoop
down and touch the surface to collect
samples the same month, but researchers
discovered that Ryugu’s terrain is unex-
pectedly rugged. The landscape is jagged
and pebbly, with no smooth powdery
areas for easy sampling, so JAXA delayed
the touchdown to ensure they could find
a safe landing spot.
It was worth the wait. On February 22,
2019, JAXA announced that Hayabusa2
had successfully descended to the aster-
oid, launched a small tantalum projectile
into the surface, and “tagged” Ryugu with
its 40-inch-long (1 m) sampler horn to
collect the resulting debris.
On April 5, Hayabusa2 upped the
ante, dropping its explosive Small
Carry-on Impactor (SCI) toward the
asteroid. As the SCI slowly descended,
the spacecraft took cover on the other
side of Ryugu, leaving its DCAM3 cam-
era about a half-mile (0.8 km) away to
observe the explosion. On April 25,
Hayabusa2 confirmed the SCI had gener-
ated a crater 66 feet (20 meters) wide,
bringing up material from beneath the
asteroid’s surface for further study.
But it took months of observing the
new crater to determine the best location
for Hayabusa2’s finale: On July 11, the
craft again swooped down to the surface,
fired its second tantalum projectile intothe crater it had created, and gathered the
results before retreating for the final time.
The spacecraft has now achieved all its
main objectives, including retrieving the4
Hayabusa2 plays tag
with asteroid Ryugu
NASA’s InSight lander took this
somewhat dusty selfie between
March 15 and April 11, using the
Instrument Deployment Camera on
its robotic arm. The white tower in
the center of the spacecraft’s deck
is its air pressure sensor; the
orange tether connects InSight to
its heat probe on the surface of
Mars. NASA/JPL-CALTECH
The Hayabusa2 spacecraft casts a shadow on the
landscape of the asteroid Ryugu shortly after the
spacecraft’s first touchdown to collect a surface
sample February 22. JAXA, UNIVERSITY OF TOKYO, KOCHI UNIVERSITY,
RIKKYO UNIVERSITY, NAGOYA UNIVERSITY, CHIBA INSTITUTE OF TECHNOLOGY, MEIJI
UNIVERSITY, UNIVERSITY OF AIZU, AIST