OPPORTUNITY: CHESLEY BONESTELL: OBSERVING: Death of a Mars Rover Master Artist of the Solar System Spots on Venus PAGE 24 PAGE 60 PAGE 52

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BLACK HOLE SHADOW

The Inside Story Page 18

SEPTEMBER 2019 skyandtelescope.com

Saunter Through Imaging URANUS AND September’s on the NEPTUNE: Planetary Nebulae High Seas Find the Ice Giants Page 30 Page 36 Page 48 THE LITTLE ROVER THAT COULD by Shannon Hall Opportunity’s

The Martian rover’s spectacular and heartbreaking saga helped rewrite End textbook knowledge of the Red Planet.

14+ 217,594 45 32 years raw kilometers degrees lifespan images traveled (steepest slope)

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5 TRACKS: NASA / JPL-CALTECH (2); OPPORTUNITY: NASA / JPL / CORNELL UNIV.; STATS: SOURCE: NASA / JPL-CALTECH The Little Rover That Could

started to exercise more extreme measures, sending Opportu- nity commands to restart its clock or communicate with the orbiters overhead by using different antennas. Nothing worked. To make matters worse, February signaled the end of the winds and the beginning of colder, darker days, even near the equator. If Opportunity didn’t stir before the seasons turned, the rover defi nitely wouldn’t after. So on the night of February 12th, scientists and engi- neers gathered at JPL where Thomas Zurbuchen, the associ- ate administrator of NASA’s Science Mission Directorate, p THE SUN GOES DARK This series of simulated images shows what announced that they would send the last commands to Opportunity would have seen as the rising dust storm blotted out a mid-afternoon sky. Each frame corresponds to a measure of atmospheric Opportunity that night. If there was still no response, he opacity, called tau, of 1, 3, 5, 7, 9, and 11. The rover survived a 2007 would declare the end of the mission. storm with a tau somewhere above 5.5 (similar to the third panel from Over the next two hours, the team sent four commands left), but the 2018 storm neared 11 (far right). streaming toward the Red Planet. And for the most part, the spirit was jubilant: People hugged colleagues they didn’t see — a hobby that ultimately landed him a job directing Oppor- often, they shared stories about the rovers, and they talked tunity to take images of the Red Planet.

about how the rover had impacted their lives. With a trip to the bar before the event and a never-ending U M A T

/

Mike Seibert, a former mission manager who left JPL in number of stories to be told, the evening was akin to an Irish H C

2017, for example, got married on the anniversary of Spirit’s wake. But when the last command was sent, the room grew E T L A

launch day. Fraeman won a contest sponsored by the Plan- deadly silent as everyone waited 27 agonizing minutes (13.5 C - L P J etary Society when she was in high school and scored a trip for the signal to reach Mars and 13.5 for a signal to return). /

A S

to JPL for the night Opportunity landed — a moment that The countdown hit zero with no news. A N

: encouraged her to become a planetary scientist. And Doug “We knew with that fi nal command, that this is it — this Y K S

Ellison (JPL) was a multimedia producer for a medical com- is over,” Harrison says. “And then a lot of people just kind of G N I N pany when he began stitching together mosaics from Spirit lost it. I stood in the corner crying, hugging Keri Bean (JPL) E K R A

and Opportunity’s publicly available images in his free time for a long time.” D

Over the course of more than 14 years, Opportunity traveled some 45 km, visiting several craters, THE TREK fi nding evidence of water-deposited bedrock, and seeing dust devils, among other sights.

Santa Maria Crater Eagle Crater

Endurance Crater Victoria Crater

26 SEPTEMBER 2019 • SKY & TELESCOPE In that moment, the team was forced to accept the inevi- “Sometimes they were recalcitrant. table. They were forced to say goodbye. Sometimes they were funny. They were More than Machine For those who see space-faring robots as gadgets of scientifi c loyal. How could you not fall in love with discovery and nothing more, it may sound strange that so them?” —JOHN CALLAS many considered the rover something analogous to a friend.

: D A N I

U R Even the most calculated scientists tend to anthropomorphize ; A A O R R M

U G Opportunity — better known as “Oppy” — and her twin, command that were harder. For more than a decade, the day- A A K T

/ C N

I A A

C Spirit. And it’s easy to see why from merely a design stand- to-day lives of these scientists had revolved around Oppor- B S

S ; , ) T H 3 S (

C

point: They were each about fi ve feet tall and outfi tted with tunity. Every morning they would check the status of the / E

L I T L S L E S A

N a robotic arm and a neck topped with two eye-like science vehicle, plan rover operations, and prepare the commands. / C

R - L L O L P C

E cameras, all eerily sentient-looking. “You really do start to feel a connection to something that’s

J

/ N

/

A R H A N O C

S But Callas notes that not only did the rovers appear more than just a machine when you spend 15 years of your O E C A Z

T I / N

L

R : A A

A human, they had human-like qualities. “They were intrepid, life making sure Opportunity is healthy, making sure her Y

S C E F - A L L O N

L P

. : they were dutiful, they were accomplished,” he says. “Some- power is okay, making sure all the commands you’re sending J A V

E I V /

B N A N O U S times they were recalcitrant. Sometimes they were funny. are good,” Fraeman says. L O / A

H G

N H T ;

: A C S They were loyal. How could you not fall in love with them?” Now, the team’s daily activities have shifted. “We come A E R S I T A S R L M M O A

And fall in love many of us did. Not only did the fi nal into work now and it’s like, ‘What do we do?’” Callas says. , T / C

U - C I H L S V P C

A

J command leave the rover team wistful, but it also inspired an “It’s dramatic change.” E D /

T /

N L L A A L A

S , E outpouring of affection from much of the world. Opportu- Seibert, who had a head start on mourning because he left C E A - N L C N R

P : N O J nity trended on Twitter for days as scientists and non-scien- in 2017, points out that the new daily routine likely won’t E

A C /

R

R / A

U U S T H

D tists alike shared stories of the rover’s impact on them. Even include the adrenaline rush that often came with working X A C N E N E E

T

T :

, L

P former President Barack Obama posted a photo of the rover’s on the rovers. “You don’t have that little dopamine hit you E N A I A L A C M G -

R L : A tracks to Instagram and congratulated the team. get when every image comes down and shows whatever you R P E K

E J E :

T / S R

T T S But for many, it was A

E R S E S A A H N T I N M the days after the fi nal Eagle Crater Endurance Crater

Victoria Crater

Santa Maria Crater

Endeavour Marathon Crater Valley Perseverance Valley

5 km Marathon Valley

skyandtelescope.com • SEPTEMBER 2019 27 The Little Rover That Could

planned the previous day was successful t FAREWELL Top: Mars Exploration Rovers and you see a new piece of Mars,” he says. project manager John Callas makes the call Already, many team members are ending the Deep Space Network’s last listen for Opportunity, February 12, 2019. Bottom: Former planning their next move. Some have mission manager Cindy Oda shares her experi- been lucky enough to fi nd jobs on other ence working on the rover that same evening. Martian projects, like Curiosity, the Insight lander, and the upcoming Mars 2020 rover. But now they have to bid but we’re talking about at least kilome- farewell to the team, too. “Opportunity ter-scale bodies of water on the surface.” is metal, glass, and silicon,” Seibert says. All in all, Opportunity drove more “But the team that became a family than a marathon on Mars — a distance to operate it — that’s what everyone is that allowed the team to not only image going to miss.” extensive features carved by long-gone lakes but to actually drive back in time. Legacy Left Behind Eagle Crater, where Opportunity landed, But while mourning Opportunity, the dates back to the Hesperian Period, 3.7 team is also celebrating her achievements. to about 3 billion years ago. In 2011 Opportunity and Spirit bounced however, Opportunity reached Endeav- onto Mars in January 2004, but their our Crater, which formed in the Noa- life expectancies were dramatically short. Engineers esti- chian Period, 4.1 to 3.7 billion years ago. It’s the oldest period mated that the rovers only had three months before so much yet studied on Mars. dust accumulated on their solar panels that they both failed Here Opportunity found signs of another ancient wet from lack of power. environment, but with water less acidic and more favorable Mars, however, intervened: Gusts of wind repeatedly wiped to life. That fi nd, coupled with Spirit’s discovery of hydrother- the solar panels clean and boosted power levels back up. That mal vents, paints a tantalizing early portrait of Mars. After allowed Spirit to last for 6 years and Opportunity to last for all, where there is both energy and water on Earth — such as more than 14. Their unexpectedly lengthy lifetimes allowed within the geysers of Yellowstone or the hydrothermal vents of them to transform our vision of Mars. the ocean deep — there is life. Throw in the organic com- Before the rovers tumbled onto the Red Planet, scientists pounds that Curiosity later found on Mars, and the Red Planet had only seen signs from orbit that Mars had hosted liquid seems to have once had everything organisms would need. water in the past. But Opportunity’s fi rst image revealed “You have the energy, you have the liquid water, you have layered bedrock, which the team determined was probably the neutral pH, you have the warm temperatures, you have sediments laid down by water. the thick atmosphere,” Callas says. “Boy, you don’t have to go Then, Opportunity stumbled upon tiny spherical grains, much further than that to say, ‘This is physically habitable to fancifully called blueberries, embedded within the sandstone. support life as we know it.’” On Earth, similar orbs form when minerals dissolved in Thanks to their extended forays, both rovers rewrote every acidic groundwater solidify again in a different form. It was textbook on Mars — and that is surely cause for celebration. further evidence that Mars was once warm and wet. “Then came the magnifi cent benefi t of the extended mis- Opportunity Lost sion,” Callas says. “As we drove this rover kilometers away “I always thought there were only two honorable ways for a from where we landed, we continued to see this evidence of mission like this to end,” says Steve Squyres (Cornell Univer- liquid water. We’re not just talking about a puddle or a pond, sity), the principal investigator and godfather of the mission.

T S A L

; ) 2 ( U

S H A C

/ E

T L

u THE LAST HURRAH This last 360° L L A E C N

panorama of Perseverance Valley com- - R L P O J C

bines 354 images taken from May 13 / /

A H through June 10, 2018. That same day, S C A E N T

: a global dust storm cut off the rover’s L G A N C I communications with Earth. The valley - L R P A J H

sits on the inner slope of Endeavour Cra- / S

A D S

ter’s rim, which rises in the distance. Had N A A

N

L :

the rover survived, it could have followed L A A M C A the valley down to the crater fl oor. E R N O O N H A P P

28 SEPTEMBER 2019 • SKY & TELESCOPE “I always thought there were only two honorable ways for a mission like this to end. One is that we simply wear the vehicle out . . . and the other is that Mars just reaches out and kills it.” —STEVE SQUYRES

“One is that we simply wear the vehicle out, and that’s what happened with Spirit, and the other is that Mars just reaches out and kills it. And that’s what happened with Opportunity. A Shortlist of Rover Discoveries To have a mission end after 14.5 years of science, being taken out by one of the worst dust storms to hit Mars in decades, Both Spirit and Opportunity penned a new story of Mars you can walk away from that with your head held high.” — one that is overfl owing with water and the necessary But no matter when a mission fi nally ends, some tantaliz- conditions to support life as we know it. Here are some of ing discovery remains just beyond reach. Indeed, Opportunity their most signifi cant discoveries. was halfway down Perseverance Valley — a feature that looked like it had been carved by water — when the dust storm hit. Acidic Waters When Opportunity fi rst landed And scientists were anxious to drive to the bottom, where 3 in Eagle Crater, the rover spotted layered bed- sediments would have gathered, to further study the crater and rock probably made from ancient sediments verify that it was indeed sculpted by water and not by wind. laid down by water. She also discovered the “It would have been the fi rst opportunity we had had to mineral hematite, which often forms in acidic look at a feature like this on the ground,” Fraeman says. water. Although scientists have spotted a number of similar gullies from orbit, they were excited to dive into one (literally) on Blueberries At the start of her the ground. If the hypothesis is true, then Fraeman suspects mission, Opportunity discov- the groundwork would have helped the team better under- ered tiny spherical grains em- stand the history of water within the region, and perhaps bedded within the sandstone. across the entire Red Planet. Those so-called blueberries It also would have painted quite a vivid picture of the Red are thought to have formed in Planet’s wet past. Callas suspects that, if it really were carved liquid water. by water, this valley might once have looked like the mag- nifi cent cascading waterfalls in Hawai‘i. And while scientists Hot Springs In 2007, Spirit p BLUEBERRIES might never answer this exact question, it points toward yet accidentally churned up The rover found these tiny mineral another legacy of the mission. silica-rich soil, which typically forms within hot spherules in April “We have made Mars familiar to the public,” Callas says. 2004. They’re “They get an idea of what it’s like to be on the surface of springs like those found in hematite-rich, and Mars. It’s no longer this strange, distant, mysterious world.” Yellowstone National Park their shape sug- Although Opportunity played a large role in this legacy, it’s on Earth. Scientists think gests they formed that our planet’s early life in an ancient, wa- not hers alone. The rover is preceded in death by Spirit, and it

E tery environment.

: might have developed in H N T

is survived by Curiosity and the Insight lander. All in all, there / O

C A

I similar environments.

N

P are eight spacecraft from the world’s space agencies currently E O R

T R U C

D

E on or orbiting Mars, with a handful set to launch next year. A J R S Neutral Waters In 2010, Spirit found rocks 10 E O S I T R L

A And that leaves scientists like Callas hopeful. He was 10 P

U 7

W times richer in magnesium and iron carbon- J

N

; : U S years old when Neil Armstrong walked on the Moon. “I was N O G

O ates than any other Martian rocks studied N S

C U I E

inspired by the Apollo program because I thought that there / H S before. Such rocks can only form in an envi- T L E

I / L

R E were no limits to what we can do,” he says. “These rovers are S R N

L ronment with neutral water. E R O B O B E continuing that inspirational legacy. It’s the Apollo program C U M

/ L Y

B S H

; of our day.” O C

T Flowing Waters In 2011, Opportunity found R E C T P E

L : J

A bright-colored veins of gypsum in the rocks N ≈ O C O R - L C P I

¢ Award-winning freelance science journalist SHANNON HALL P near the rim of Endeavour Crater. Because J N E

/ U M

O A A still tears up when watching the video of Opportunity’s suc- the mineral likely formed when water fl owed N L S

F A

E ; N H T cessful landing.

: through underground fractures in the rocks, it T C

S / E

E J I H R O was the fi rst sign of fl owing water. A R R B E P

B B A N Read the team’s favorite stories from the mission: jpl.nasa.gov/ E H U U A O L

B M N opportunity-memories.

skyandtelescope.com • SEPTEMBER 2019 29