Megan Knapp

Opportunity

3/7/2019

From Surface to Science

Ethan Gower / For The Post (and for Mars)

In early 2004, a pair of explorers began their journey across Mars. The Mars Exploration Rovers Spirit and Opportunity – MER-A and MER-B, respectively – rolled over opposite sides of the planet. The goal of the rovers: follow the water, and with it, decipher the history of Mars.

For all of its ocher shades, Mars is cold. On a summer day, temperatures reach only about -10º Fahrenheit. This is troublesome for robots, especially when their solar-powered electronics could freeze.

“That was the key thing: you gotta keep them warm or else circuits break in that cold environment,” Keith Milam, associate professor of geology, said.

As one of the scientists on the MER missions, Milam was aware of the logistics of keeping rovers alive in the cold.

“As Martian winter is coming, find a slope, park on (it) with the solar panels angled towards ... the Sun,” Milam, who is a professor of the reporter, said. “If you couldn’t get into that position … the onboard batteries wouldn’t last the martian winter.”

Unable to warm itself, Spirit froze in 2010.

Opportunity recently joined its companion after losing power during a dust storm in the summer of 2018. The last message received from the rover was “my battery is low and it is getting dark,” or at least that’s how the transmission was translated.

“I think it’s really been personified,” Emily Simpson, a senior studying geology, said. “It’s sad that it’s gone, but it’s not the end of (Mars exploration).”

Riley Scott | FOR THE POST

Opportunity pokes out its head

A common theme of endings to Mars missions seems to be dust storms coating the solar panels and choking the mission prematurely. That is, of course, if one can consider a mission running 60 times longer than expected to be premature.

“We actually knew fairly early on that at least one of the rovers might go on for a while,” Milam said.

He was involved with the mapping of Spirit’s landing site, Gusev crater, where dust devils had been seen from orbit as dark streaks where the whirlwind scoured dust off the surface. As the dust devils neared Spirit, accumulations on its solar panels were wiped clean.

Opportunity was less fortunate, but the prevailing winds in the rover’s landing site, Meridiani Planum, helped keep its panels clear.

While wind was good for mission length, the same could not be said for the scientists working on it. For the MERs, NASA brought in teams for three weeks in Pasadena, California, with one week off. This was realistic for a mission lasting about 90 days, but with the wind, the missions could potentially last several years.

“(We were) all planning for maybe a few months of activity, but now what? These rovers could literally outlive some of the people on the mission,” Milam recalled.

Longevity aside, the MER missions provided invaluable information of the physical processes on Mars – in particular, how, and when, water was present near the surface. The craters interspersed within Meridiani Planum punched through the martian surface, exposing the older rock underneath. The layering of sediment in Meridiani gave scientists insight into the transition from an early, wet Mars to the desert Mars seen today.

Those findings were secondary to the primary mission, which was to find the iron oxide, hematite, that generally forms in the presence of water. As water moves through the porous sandstone, small spherules of hematite can form and grow to about the size of a BB. As the sandstone weathers away, the more resilient iron oxide is left behind, along with small volcanic rocks. The collection of spherules, gray against a ruddy background, look like tiny blueberries.

Opportunity and the other Mars explorers laid the foundation for subsequent missions. Curiosity operates in much the same way as MER-B, using its onboard instruments to collect data in search of hydrous minerals. The Mars 2020 rover follows suit and, once it lands, will look at salty and possibly acidic water and water ice, Simpson said. Both rovers differ from the MERs in that they are powered by radioactive decay of polonium, rather than by solar panels.

“Curiosity has the potential, as long as its hardware can take it, of lasting much longer than Spirit or Opportunity,” Milam said.

Exploring Mars has afforded planetologists the chance to put their hypotheses to the test with a rapidity never seen before.

“In planetary science, very often, people write about faraway places that spacecraft, in your lifetime, will never visit,” Milam said.

In his case, his interpretations of Gusev crater were scrutinized mere weeks after publication. The pay off, Milam said, was to be the one to download whatever data came back from the rovers, knowing he was the first living thing to view that piece of Mars.

“There’s something special about that,” he mused.

As for the rovers themselves, and indeed all Mars missions, the question remains: what will be done once humans visit the red planet? Simpson is of the opinion of placing the rovers in a martian museum.

“It won’t be fresh in [colonizers’] minds, so it’s important to talk about what we were able to learn and what the scientists … were able to accomplish.” Simpson said.

Milam holds a different opinion, one more sentimental. He believes that the rovers should be left as they are – conserved, not preserved.

“You shouldn’t have people traipsing around [the landing sites],” Milam said, nor should they be taken back to Earth. “They were built for Mars, they’re Martians. They need to be there.”

Development by: Ryan Vallette / For The Post