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 native, couldn't be happier to see his hometown 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."
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 Mount Sharp at the center of the 96-mile-wide Gale Crater since August 2012.
Curiosity happened on the 3-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 email. "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."
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.
Curiosity has been gradually climbing up Mount 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.
Wiens' specialty is the rover's ChemCam, an instrument able to study soil and rock at a distance using a laser.
"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.
"The drill is using new software and commands that work around a few issues ... over the last 15 months. That software has been tested extensively, but what happens on Mars is a bit of an experiment," Wiens said. "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," Wiens said.
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.
News Tribune reporter Brooks Johnson contributed to this story.