Sky & Telescope - September 2019 - 25

he Martian winds were picking up - kicking dust, sand,
and debris off the ground in a storm that would soon
envelope the entire globe.
For weeks, amateur astronomers on Earth would swing
their telescopes toward the Red Planet only to ﬁnd its familiar
surface features hidden under a thick veil of dust. The many
satellites that orbit Mars would similarly image a hazy globe.
And a beloved rover on the surface would fail to see the Sun,
as daytime temperatures plummeted and the winds pummeled against it. Opportunity was in the heart of the storm.
On June 10, 2018, when the storm was well underway,
NASA scientists asked the rover to take two photos of the
Sun. But the images revealed nothing more than the faintest
pinprick of light surrounded by a blackened sky. "By the time
the dust storm was at its strongest, it was as dark for Opportunity at noon as it would be on a moonless night here on
Earth," says Tanya Harrison (Arizona State University). "I'm
not sure we can even fathom a storm that severe on Earth -
that just could completely black out the Sun."
Little did scientists know at the time, those two photos
would be Opportunity's last. After the rover transmitted the
images to Earth, it hunkered down for the dust storm. Scientists on Earth waited, hopeful that once the storm cleared the
rover would pop back to life. But the intrepid explorer never
stirred. In February 2019, NASA declared the mission complete.
"It's almost like the death of a loved one," says project
manager John Callas (Jet Propulsion Laboratory). "You're
used to seeing that individual every single day and interacting
with that individual. You have meals with them. You live your
day with them. Suddenly, they're gone."

T
"Opportunity had gotten
through a lot of tough
scrapes before, so we
learned never to bet
against the vehicle."
-ABIGAIL FRAEMAN

tp THE ROAD TRAVELED Opportunity looks back on its own
tracks on two days in 2010: May 8th (far left) and August 4th
(above). An artist's concept sits between.

Unaware of the coming tragic ending, the mood last September was hopeful - optimistic even - with many scientists
expecting that the rover would pull through. "Opportunity
had gotten through a lot of tough scrapes before, so we
learned never to bet against the vehicle," says deputy project
scientist Abigail Fraeman (JPL). "Anything is possible."
In the best-case scenario, the rover would simply wake up
and phone home. "We were hoping that all we really had to
do was wait and listen, and we were listening every day," Callas says. More likely, however, was a scenario in which heavy
dust had settled onto Opportunity's solar panels, blocking
the Sun and preventing the rover's batteries from recharging.
Here, too, scientists had hope: They expected that a heavy
wind would clear away any settled dust, allowing the rover to
rouse from its deep slumber.
But when the silence stretched into January, the team
started to worry, convinced that there was another issue. It
was possible that the rover's internal clock had stopped keeping track of time. This would be a serious problem, because
Opportunity wouldn't know when to go into deep sleep at
night and would instead just burn through the battery. Or
perhaps one of the radio antennas was broken and the rover
couldn't send signals home, even if awake. So the team
sk yandtele scope.com * S E P TE M B E R 2 019

TR ACKS: N ASA / JPL- CA LTECH (2); OPPORT UNIT Y: N ASA / JPL /
COR NELL UNIV.; STATS: SOURCE: N ASA / JPL- CA LTECH

The Long Goodbye

http://www.skyandtelescope.com

Sky & Telescope - September 2019

Table of Contents for the Digital Edition of Sky & Telescope - September 2019