10 ASTRONOMY • MAY 2020
QUA NTUM GRAVITY
The blinding f lash of light
came first, followed by a shock
wave and massive earthquake. Only
later did the hailstorm of black, glassy
debris begin, a rocky rain that fell on
10 percent of Earth’s surface.
That’s the scene that followed a mas-
sive asteroid impact 790,000 years ago.
The rocky remains it scattered, called
tektites, have been found from Asia to
Antarctica. For decades, scientists have
searched for the elusive resting place
of the impactor. And now, they think
they’ve found it.ELUSIVE CRATER
A report published January 21 in the
Proceedings of the National Academy
of Sciences says that the meteorite
likely struck in the Bolaven Plateau in
southern Laos, carving a 10.5-by-8-mile
(17 by 13 kilometers) crater that’s now
covered by an ancient lava f low. Afteridentifying the potential impact site via
satellite imagery, researchers excavated
the area and found the lava dated to
around the same time as the impact,
while the surrounding sediments were
older. This evidence was bolstered by
gravity measurements that hinted at
a crater hiding below.
By finding the site of the asteroid
strike, researchers have been able to
reconstruct some of the chaos that
ensued after the impact, says study
co-author Kerry Sieh, a geologist at
Nanyang Technological University
in Singapore. The finding could also
illustrate some of what we could expect
if a similarly large asteroid were to
strike Earth again.ANATOMY OF AN APOCALYPSE
Roughly 1.25 miles (2 km) wide, the
impacting rock would have gouged
a hole larger than San Francisco injust seconds. The meteorite’s speed
and force would have been enough to
send pillow-sized boulders careening
through the air at almost 1,500 feet
(460 meters) per second — faster than
the speed of sound. “It would not
have been a healthy thing to be on the
receiving end of that,” Sieh says.
Next, Sieh wants to focus on some
of the ashy material surrounding the
meteor’s debris. The impact would
have incinerated all plant and animal
life within 300 miles (480 km) of the
impact site, and Sieh is curious how
that kind of settling dust would affect
all of us today, if such an event were to
occur in modern times.
The odds of such an impact in our
lifetimes are extremely low, but the
prospect still fascinates Sieh. “I’ve never
worked on meteorites before,” he says,
“but I got sucked into this with my
curiosity.” — LESLIE NEMO, JAKE PARKSFOUND: CRATER FROM
790,000-YEAR-OLD ASTEROID STRIKE
The massive but elusive impact rained down ash over 10 percent
of Earth’s surface, leaving a mark far beyond the site of the hit.
INCOMING. Large asteroids rarely end up
on a collision course with Earth. But smaller
impactors, like the one seen in this artist’s
concept, can still wreak havoc around the
world. URIKYO33 (PIXABAY)