2019-06-01+Sky+and+Telescope

NEWS NOTES

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ON FEBRUARY 21ST, the Japanese

spacecraft Hayabusa 2 grabbed its fi rst

sample from the asteroid 162173 Ryugu,

the asteroid it has been orbiting since

last summer (S&T: Oct. 2018, p. 11).

Immediately after the craft touched

down, it fi red a tantalum bullet at the

asteroid’s surface and knocked away

material that fl ew up into a sampling

horn. Then the spacecraft took off

again. Hayabusa 2 has now sealed the

sample collection compartment, saving

the sample for return to Earth.

Finding the right spot to sample

Ryugu was more challenging than

anticipated. When Hayabusa 2 arrived

at Ryugu on June 27, 2018, it found

a uniformly rocky asteroid with no

smooth areas on which it could alight.

The team had to develop new sampling-

site selection criteria, identifying two

extremely narrow locations where

they’d have to navigate the spacecraft

between boulders. The team tried out

descending toward those sites twice.

Back on Earth, they also tested whether

the bullet-fi ring mechanism would

liberate enough material from a rocky

surface. Testing went well, so the team

proceeded.

The spacecraft has no way of mea-

suring just how much material made

it into the collection chamber, so we

won’t know for sure what Hayabusa 2

has collected until it returns to Earth.

However, all the spacecraft telemetry

are consistent with success. The mission

allows for two additional attempts at

sample collection, though the mission

team still has to decide whether obtain-

ing another one would be worth the

added risk.

Hayabusa 2 also has one more exper-

iment to perform: its Small Carry-on

Impactor (SCI), a probe that will carry

explosives to accelerate a 2-kg copper

lump at Ryugu’s surface in an attempt

to create an artifi cial crater. Hayabusa 

will shelter from the impact behind

the asteroid’s bulk, but before it hides,

it will deploy a camera to watch in its

place. The spacecraft will then emerge

to pick up surface debris. Being able

to directly compare material from the

asteroid’s weathered surface to its rela-

tively pristine interior would be a boon

to scientists, who must often determine

bulk composition from remote observa-

tions of asteroids’ surfaces.

Hayabusa 2 will remain in proximity

to Ryugu until November or December.

Its return will take about a year. After

dropping its sample in the Australian

desert in December 2020, the spacecraft

could potentially extend its mission to

fl y past another asteroid.

■ EMILY LAKDAWALLA

SOLAR SYSTEM

Hayabusa 2 Touches Asteroid, Collects Sample

MARS

Opportunity Reaches

the End of the Road

pHayabusa 2 took this picture of Ryugu as

the spacecraft began ascending after its brief

touchdown. Hayabusa 2’s shadow can be seen,

along with a dark splotch where the space-

craft’s thrusters blew away lighter materials on

Ryugu’s surface.

tNASA’s Opportunity rover looked back over

its own tracks on August 4, 2010.

NASA FORMALLY ANNOUNCED the

end of the Opportunity mission on

February 13th. The team last contacted

the rover on June 10, 2018, days before

a dust storm enveloped the planet and

likely coated the rover’s solar panels,

cutting off its power supply. The storm

was both darker and longer than one

that Opportunity had weathered in

2007. The team attempted to make con-
      tact over the following eight months,

10 JUNE 2019 • SKY & TELESCOPE