Mars Rock Named For Duluth

NASA’s Mars Curiosity rover took this photo of the rock named Duluth on May 15. The block is about 3 feet long. This isn’t the first time “Duluth” has appeared on Mars. The name was first used on a ChemCam laser target several years back. Normally names are used just once, but the mission team made an exception. NASA / JPL-Caltech

Meet Duluth, a desk-sized chunk of rock once lapped by the waves of an ancient Martian lake. Roger Wiens, 58, the project leader for the ChemCam instrument on the Mars Curiosity rover and Duluth, Minnesota native, couldn’t be happier to see his home town chosen as the name of the 3.5 billion-year-old slab of sedimentary rock.

“Duluth has one of the coolest climates in the U.S. due to its proximity to the world’s largest and one of the deepest freshwater lakes,” Wiens wrote in a recent blog. “The drill target “Duluth” on Mars was also once near the shore of a large freshwater lake. Its climate is also relatively cool, so the name is apropos.”

Gale Crater is home to NASA’s Curiosity rover, marked by the red dot. Mount Sharp, the broad rise in the crater’s center, is a 3-mile-high mound of sediments laid down billions of years ago when a large lake occupied the crater’s center. NASA / JPL-Caltech

The name was chosen to recognize the Duluth Complex, a vast underground arc of crystalline volcanic rock called gabbro that forms the bedrock of the city and much of northeastern Minnesota. What better place for our craggy town to find an interplanetary connection than on Mars, a rusty-red world of endless rocky vistas and tall volcanoes. The layered, sedimentary rock caught the eye of the mission team studying photos returned by NASA’s Mars Curiosity rover, which has been exploring the slopes of Mt. Sharp at the center of 96-mile-wide Gale Crater since August 2012.

This spectacular image of a Martian butte made of layers of sandstone in the Murray Foundation on the lower slopes of Mount Sharp was taken in 2016 by the Mars Curiosity rover. NASA/JPL/MSSS/Ken Kremer/ Di Lorenzo

Curiosity happened on the three-foot-wide block earlier this week while exploring the lower slopes of the mountain called the Murray Formation, a 1,000-foot-thick layer of rock formed from sediments that accumulated on the floor of an ancient lake.

“It appears to be almost entirely lake-bottom sediments,” said Wiens in an e-mail. “A fair amount of this sedimentary rock has been relatively soft, and it consists of very thin layers about a millimeter (1/25th of an inch) thick. The large number of layers suggests that the lake was there a long time.”

This fisheye view of Duluth Rock was taken by the rover’s hazard-avoidance camera. NASA / JPL-Caltech

Just as Duluth huddles along the shore of Lake Superior, its namesake on Mars once lined the shore of a lake from the planet’s more clement past, when the climate was more Midwestern than Antarctic.  Several billion years ago, Mars had a thicker atmosphere, warmer temperatures and fresh water that pooled in lakes and rushed through now-dry riverbeds.

Mars is a rugged little planet about twice the size of our moon. This photo, taken on May 15, shows Duluth Rock (bottom center) in the context of the Martian landscape and Murray Formation. NASA / JPL-Caltech

Curiosity has been gradually climbing up Mt. Sharp, studying rocks and soil and taking pictures along the way, looking for clues as to whether the planet was habitable in the past. Water is crucial for life. Gale Crater is loaded with old sediments, pebbles rounded by running rivers, ancient clay and mudstones. Since arriving in August 2012, the rover has climbed almost a thousand feet in elevation. Now that it’s reached that choice lake shore property, scientists are eager to study the area in greater detail.

Roger Wiens poses with a life-size replica of the Curiosity rover around the time of its launch in November 2011. NASA / JPL-Caltech

Wiens’ specialty is the rover’s ChemCam, an instrument able to study soil and rock at a distance using a laser.

ChemCam did a 3×3 series of laser zaps on a smooth part of “Duluth”. You can see 8 of the 9 laser pits above — the other laser burst hit a small pebble. The image covers an area 2 inches across. NASA / JPL-Caltech

“We fire a laser beam at rocks and soils and look at the flash that we create by that laser and determine the composition of rocks and soil,” he said. The laser vaporizes a bit of rock into a whiff of hot, glowing gas that gives off certain colors according to the elements of which it’s made. Zapping started this week on two small patches of the rock nicknamed “Pine Mountain” and “Windigo.” Yes, spots on chosen Mars rocks get names too, even if they’re officially unofficial until approved by the International Astronomical Union.

Curiosity is also equipped with a drill that’s unfortunately been on the fritz for more than a year, but there’s hope a fix in the works will see it fire up just in time to investigate the Duluth block.

Mission control prepares the drill at the end of Curiosity’s robotic arm to take a sample of Duluth Rock this weekend. Soil around the rock shows wind-blown ripples. NASA / JPL-Caltech

“The drill is using new software and commands that work around a few issues … over the last fifteen months. That software has been tested extensively at JPL, but what happens on Mars is a bit of an experiment,” said Wien in an e-mail. “The rover must do its drilling while it is out of contact with Earth. We’ll find out Monday how it all went!”

Keep your fingers crossed. If the drill works and we get a “bite” from our special slab, Curiosity will place it inside its mobile laboratory to study it in greater detail in hopes of cracking the door open a little more on whether Mars may have been an abode for life.

“We’re expecting to operate for several more years and climb further up the side of this mountain in the middle of the crater, shores of the lake if you will,” said Wiens.

Although it looks like so many layers of crumbling paint, Duluth Rock is quite solid: “We don’t want the rock to shift during the drilling operation,” said Wiens. NASA / JPL-Caltech

When that mission is over, Wiens will be in charge of the new SuperCam instrument on the Mars 2020 rover slated to launch to the Red Planet in July 2020. The instrument will examine rocks and soils up close, looking for organic compounds that could be related to past life on Mars. For now, Duluth, always a popular destination with tourists no matter which planet it calls home, is getting all the attention. Deservedly so.