By Tim Johnson · Wednesday, June 22, 2016 – Reprinted from CascadiaWeekly.com
Life. Are we unique? Are we alone? These are time-honored questions, and the answers may be approaching. Our best candidate for exploration is one of our nearest neighbors, Mars, a small, cold desert world that might have had a vibrant and watery past. The surface of Mars is currently being explored by robots, some long past their expected engineered lives. Each has advanced scientific understanding of the surface of Mars. Soon they’ll be joined by another, designed to advance the discoveries made by other devices and instruments and tuned to a specific mission: The search for signs of life, past or present, on the Red Planet.
Some of the world’s top Mars scientists will gather in Bellingham to share the latest scientific results from Mars exploration and preview NASA’s next-generation Mars rover mission. While they’re here, they’ll also visit the extensive lava flows in the eastern portion of the state, a model for the types of geological features and terrain that might be expected on Mars.
The group includes Jim Bell, the lead scientist on the next-generation camera system that will fly on NASA’s next Mars rover, which is scheduled to launch in 2020. Working on that device is Western Washington University’s Melissa Rice, assistant professor of Geology and member of three NASA Mars rover missions, will engage a dynamic panel on the future of human and robotic exploration of the Red Planet. She will lead a panel discussion that includes Bell, engineer Justin Maki of NASA’s Jet Propulsion Laboratory, planetary evangelist and educator Emily Lakdawalla of the Planetary Society, and former NASA Shuttle astronaut Wendy Lawrence. Retired Navy Captain Lawrence serves as an advisor to the University of Washington.
“There has been a revolution in our understanding of Mars as a potentially habitable world over the past two decades, and this next mission is our most ambitious yet,” Rice said. “The first real robot geologists on Mars were the Mars exploration rovers—the two twins, Spirit and Opportunity,” Rice explained. “They landed on Mars in 2004 and their main goal was to search for signs of how water had interacted with rocks on the surface of Mars. They were built when NASA’s main goals were to follow the water, search for where water had been or is currently in the solar system.”
Opportunity had a primary mission life of 90 days. It is still operating on the surface of Mars, 12 years later—a testament to rugged engineering. Curiosity, a car-sized robotic rover built to explore Gale Crater on Mars, began its mission in 2012. It completed its primary mission in two years, and is still roving. The Planetary Society continues to issue updates on its journey.“Curiosity took it a step further,” Rice noted. “Curiosity wasn’t just looking for signs of water. Curiosity was looking for signs of habitability—which is not just water but all of the other conditions that are required for life. “Life needs water, but life needs a certain kind of water, life needs water that is not too acidic, that’s not too salty, and water that’s actually been around on the surface of Mars for long enough to sustain organisms,” she said.
Discoveries from each mission has influenced the profile of the next, informing the engineering and refining and narrowing what scientists seek. “It’s really the Curiosity mission having found evidence for habitable past environment that paved the way for this next mission,” Rice explained. “Curiosity, for example, landed next to some rocks that the rover drove up to and drilled into, and found they were mudstone rocks, formed at the bottom of an ancient lake. We can tell from the chemistry of the minerals that are preserved in that rock that the water in that ancient lake where these rocks formed would have been good enough to drink—it wasn’t acidic, it wasn’t too salty.”
Conditions on ancient Mars—which may have had a heavier, warmer, wetter atmosphere, and which may have had a magnetic field shielding the surface from radiation—may have permitted life. “This next rover is a big step because it is the first NASA mission at Mars to be directly looking for signs of life, not just the conditions for life but actual signs of past life,” Rice explained. “We’re searching for what are called bio-signatures, which is any piece of evidence that could exist in the rock record on Mars for past organisms having been present on the surface,” she said.
Bio-signatures, this evidence for life, could exist in many forms. “The most obvious thing that we would love to see would be something like a dinosaur bone sticking up out of the ground. That would be an obvious bio-signature!” Rice said. “But, more realistically, what a bio-signature on Mars would look like is a concentration of organic molecules, which are the building blocks of life; or perhaps an isotopic signature—chemical isotopes that have been segregated by processes that can only be explained by having life forms present; or minerals that are only created by living organisms; or micro-fossils—very, very small structures preserved in the rock that indicate signs of previous life forms.”
Bell, Rice and their team are crafting the instruments that will be used to search for those signatures, a suite of devices installed on a long neck at the front of the 2020 rover, a camera mast. Their team is at work on the pragmatically named Mastcam-Z. “Mastcam-Z is a set of two twin cameras that are going to serve as the two eyes of the rover,” Rice explained. “We will be able to take stereo images both zoomed out, wide field of view, and zoomed in at very high resolution. “The other capability that Mastcam-Z has, and what I am most involved with,” Rice noted, “is multi-spectral capabilities. Each of the zoom lenses will also have a filter wheel in front of the camera’s detector. The filter wheel is basically a circular disk with eight holes in it. Each hole will contain a filter of a different material that allows a different set of wavelengths pass through. “We’ll have clear filters for when we just want to take a quick point-and-shoot image that will look more like what an image would look like if you took a picture on Mars with your iPhone,” Rice said. “But in other positions on that filter wheel we can take an image that is only in red wavelengths—or blue, or green—so we can sample specific parts of the visible spectrum. We can also take images in near-infrared wavelengths as well, beyond the spectrum visible to the human eye.
“That’s important and exciting,” Rice said, “because Mars is pretty bland-looking in visible wavelengths. Pretty much everything on the surface of Mars is some shade of reddish-brownish-orange. But in the infrared Mars is a much more colorful place. “The near-infrared wavelengths that we will have filters designed to capture are sensitive to subtle differences in iron-bearing minerals, but also some sensitivity to color differences in hydrated minerals as well—minerals that contain water in their structure.
While its mission is specific, the 2020 rover (which does not yet have an official name) will also gather other evidence on the geology and history of Mars. “We have a good sense of the range of geological processes that have occurred on Mars, but there are still some very basic questions about the geology of Mars that we don’t have answers to,” Rice admitted. “For example, there are areas on Mars that show evidence of remnant magnetic polarization, which means that when the rocks formed they froze in the direction of Mars’ early magnetic field. But Mars doesn’t have a magnetic field today. “When Mars’ magnetic dynamo shut off, and why, and how long that process took—those are some very basic geophysical problems that we still don’t have answers to.”
But what portion of Mars will the rover explore? That also hasn’t been decided yet, but the field is narrowing. “We are interested in finding a landing site for this rover where we can answer these questions about past life, but also get at some of these big-issue Mars questions as well,” Rice said. Thirty sites had been under consideration until last August, when NASA held a landing site workshop where scientists and engineers from all over the world gathered in Southern California. “At the end of that meeting there was a vote, and the top eight winners of that vote got to move forward for the next round of analysis. Three of those eight were also finalist landing-site candidates for the Curiosity rover mission. Some of these sites have been under consideration for missions for many, many years now.
“About half of these eight sites are places where there is very good evidence for long-lived standing bodies of water. Three of the other sites are a little different, they don’t have as much direct evidence for lakes at the surface but they show—mainly through their mineralogy that we can detect from orbit—evidence for deep crustal alterations, something like hydrothermal fluids altering the crust underneath the surface. “Those sites are from some of the oldest terrain on Mars.”