10 ASTRONOMY • JUNE 2020
QUANT UM GR AVIT Y
New data from the first spacecraft to softly
land on the lunar farside are offering fresh
details about the part of the Moon that’s
hidden from view from Earth.
China’s Chang’e-4 lander, equipped
with the Yutu-2 rover, touched down in
January 2019 inside Von Kármán crater, a
large impact site nestled inside the South
Pole-Aitken Basin. The 1,600-mile-wide
(2,575 kilometers) basin is the widest,
deepest, and oldest such feature on the
Moon. It is also a prime target for sci-
entists who want to study our satellite’s
evolution over billions of years.
Yutu-2 probed below the surface using
ground-penetrating radar, which sends
pulses through the Moon’s subsurface and
measures the signals that reflect back. It
found that the landing site is carpeted with
loose dirt, called regolith, up to 40 feet
(12 meters) deep, according to a paper pub-
lished February 26 in Science Advances.NASA astronauts and experiments, as
well as the Soviet Luna missions, showed
that this pulverized dust and rock is preva-
lent across the Moon’s nearside. But sci-
entists weren’t sure if the same material is
spread across the rest of the satellite.
Yutu-2 also looked beneath the surface
regolith. Farther down, the rover found
alternating layers of boulders and large
rocks interspersed with finer soil to depths
of roughly 130 feet (40 m). Each of those
layers of boulders was probably deposited
as space rocks hit the Moon’s surface
and filled the air with ejecta. Although the
radar couldn’t see any deeper, the scien-
tists suspect this pattern continues.
The mission’s results will ultimately help
scientists better understand the Moon’s
formation and evolution. Astronomers also
say that studying craters on the Moon can
provide a proxy for what happens when
large objects strike Earth. — E.B.Chinese rover peers
beneath the lunar farside
SOLAR
ORBITER
HEADS FOR
THE SUN
On the night of February 9,
the European Space Agency
and NASA successfully
launched their joint Solar
Orbiter mission from Cape
Canaveral Air Force Station
in Florida aboard a United
Launch Alliance Atlas V
rocket. During its mission,
Solar Orbiter will get up
close and personal with the
Sun to investigate our host
star and its magnetic field,
as well as how the solar
wind that inf luences our
solar system is generated.
It will take the spacecraft
about two years to reach
its targeted science orbit;
once in place, it will be
well positioned to study
the Sun’s poles up close for
the first time. The mission
will also work in conjunc-
tion with the Parker Solar
Probe, which launched in
2018 and has already made
several record-setting close
approaches to our star.
— H.R.M., ALISON KLESMANUNEXPLORED
TERRAIN. The
Chang’e-4 lander
took this image
of the landscape
near its landing
site on the lunar
farside. Based on
data from the
mission’s Yutu-
rover, the entire
Moon may be
covered in a
deep layer of
fluffy dust called
regolith. NAOC/CNSA JA
REDFRAN
KLE,^ NASA^
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