M17 archa 2022 was a difficult day for Jorge Vago. A planetary physicist, Vago heads science for part of the European Space Agency’s ExoMars program. His team was just months away from launching Europe’s first rover, a goal they had been working toward for nearly two decades. But on that day, ESA suspended its ties with the Russian space agency because of the invasion of Ukraine. The launch was planned for Kazakhstan’s Baikonur Cosmodrome, which is leased by Russia.
“They told us we had to stop everything,” Vago says. “We were all grieving.”
It was a painful setback for the beleaguered Rosalind Franklin rover, originally approved in 2005. Budget problems, changing partners, technical issues and the Covid-19 pandemic have in turn caused previous delays. And now war. “I’ve spent most of my career trying to get this thing off the ground,” Vago says. Further complicating matters, the mission included a Russian-made lander and instruments that ESA member states will need funding to replace. They are considering many options, including simply putting the unused rover in a museum. But then, in November, a lifeline came when European research ministers pledged 360 million euros to cover the cost of the mission, including replacing Russian components.
When the rover finally, hopefully, launches in 2028, it will carry an array of advanced instruments — but one in particular could have a huge scientific impact. Designed to analyze any carbon-containing material found beneath the surface of Mars, the rover’s next-generation mass spectrometer is the foundation of a strategy to finally answer the Red Planet’s burning question: Is there evidence of a past or present life?
“There are many different ways you can look for life,” says analytical chemist Marshall Seaton, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory and co-author of a paper on planetary analysis in Annual Review of Analytical Chemistry. Perhaps the most obvious and direct route is simply to look for fossilized microbes. But non-living chemistry can create deceptively realistic structures. Instead, the mass spectrometer will help scientists look for molecular patterns that are unlikely to form in the absence of living biology.
Hunting for patterns of life, rather than structures or specific molecules, has an added benefit in an alien environment, Seaton says. “It allows us not only to search for life as we know it, but also for life as we don’t know it.”
(CREDIT: ESA / ATG MEDIALAB) Artist’s rendering of the Rosalind Franklin rover.
Packing for Mars
At NASA’s Goddard Space Flight Center outside Washington, D.C., planetary scientist William Brinkerhoff displays a prototype of the rover’s mass spectrometer, known as the Mars Organic Molecule Analyzer, or MOMA. About the size of a carry-on suitcase, the instrument is a maze of wires and metal. “It really is a workhorse,” Brinkerhoff says as his colleague, planetary scientist Xiang Li, adjusts the prototype’s screws before demonstrating a carousel that holds samples.
This working prototype is being used to analyze organic molecules in Mars-like soils on Earth. And once the real MOMA reaches Mars, around 2030, Brinkerhoff and his colleagues will use the prototype — as well as a pristine copy stored in a Mars-like environment at NASA — to test tweaks to experimental protocols, fix problems that arise during the mission and to facilitate the interpretation of data from Mars.
This latest mass spectrometer can trace its roots back nearly 50 years, to the first mission to explore Martian soil. For the twin Viking landers of 1976, engineers miniaturized room-sized mass spectrometers to roughly the size of today’s desktop printers. The instruments have also been aboard the Phoenix lander since 2008, the Curiosity rover since 2012, and later Mars orbiters from China, India and the United States.
Anyone who visits the Brinkerhoff prototype must first pass a display case with a disassembled replica of the Viking instrument on loan from the Smithsonian Institution. “It’s like a national treasure,” Brinkerhoff says, enthusiastically pointing out the components.
(Credit: CARMEN DRAHL) At NASA’s Goddard Space Flight Center, William Brinkerhoff stands next to a working prototype of the Rosalind Franklin mass spectrometer.
Mass spectrometers are indispensable tools used for analytical chemistry in laboratories and other facilities around the world. TSA agents use them to test luggage for explosives at the airport. EPA scientists use them to test drinking water for contaminants. And drug makers use them to determine the chemical structures of potential new drugs.
There are many types of mass spectrometers, but each “is a three-part instrument,” explains Devin Swinner, an analytical chemist at the pharmaceutical company Merck. First, the tool vaporizes the molecules in the gas phase and also gives them an electrical charge. These charged or ionized gas molecules can then be manipulated with electric or magnetic fields so that they move through the tool.
Second, the instrument sorts ions using a measurement that scientists can relate to molecular weight so they can determine the number and type of atoms a molecule contains. Third, the tool records all the “weights” in the sample along with their relative abundances.
With MOMA on board, the Rosalind Franklin rover will land on a Martian site that, about 4 billion years ago, likely contained water, a crucial ingredient for ancient life. The rover’s cameras and other instruments will help select samples and provide context for their environment. A drill will extract ancient samples from a depth of up to two meters. Scientists assume that’s far enough away, Vago says, to be shielded from Mars’ cosmic radiation, which breaks down molecules “like a million little knives.”
Space mass spectrometers must be strong and light. A mass spectrometer with MOMA’s capabilities would normally take up multiple desks, but it is significantly compact. “To be able to take something that could be as big as a room down to the size of a toaster or a small suitcase and send it into space is a very big deal,” says Swinner.
(CREDIT: ESA / THALES ALENIA SPACE) The Rosalind Franklin rover’s drill, pictured here in simulated Martian terrain, can reach up to two meters below the surface of Mars, deeper than any other rover has attempted on the Red Planet. It will provide samples for the rover’s mass spectrometer to examine for signs of life.
The view of life
MOMA will help scientists look for telltale signs of life on Mars by sifting through molecules for patterns unlikely to form otherwise. For example, lipids—compounds that comprise the building blocks of cell membranes—have a preponderance of even numbers of carbon atoms in almost all living things, while nonliving chemistry produces a more even mix of even and odd numbers of carbon atoms. Finding a set of lipids with carbon atoms that are multiples of a number—rather than a random assortment—is a potential signature of life.
Likewise, amino acids—the building blocks of proteins—can be created either by life or by nonbiological chemistry. They come in two forms that are mirror images of each other but are otherwise identical, such as left and right handed. On Earth, life predominantly contains only left-handed amino acids. Inanimate chemistry makes both left- and right-handed varieties. In other words, a large excess of left or right amino acid is more realistic than a more even mixture.
More generally, scientists believe that chemical distributions like these would be indicative of life even if the molecules showing the patterns did not exist in Earth’s biochemistry.
Previous Mars missions that included mass spectrometers ran into problems that hindered their ability to identify signs of life. Scientists took these hard-earned lessons and designed MOMA to overcome these obstacles, including one of the most worrisome: the notorious molecule destroyer, perchlorate. Perchlorate, which also occurs in extreme terrestrial environments such as that of South America The Atacama Desertit can break down organic molecules at high temperatures, obscuring potential signs of life.
In 2008, the Mars Phoenix lander detected perchlorate ions in the Martian soil. Two other missions, the Viking lander and the Curiosity rover, detected chlorinated hydrocarbons — possible byproducts of perchlorate reacting with Martian molecules in the high-temperature furnaces of their mass spectrometers. This meant that the perchlorate may have hidden any evidence of organic molecules that might indicate life.
MOMA cleverly circumvents the perchlorate problem with an ultraviolet laser. The laser vaporizes and ionizes the samples simultaneouslywith light pulses lasting less than two nanoseconds—too fast for perchlorate reactions to occur.
The laser has another advantage: it leaves the molecules largely intact when it gives them a charge to create ions. Viking and Curiosity generated ions by bombarding them with electrons. These collisions do not preserve weak chemical bonds, which can be important for determining the structures of molecules in a sample, while the laser keeps molecule fragmentation to a minimum. MOMA can then sort through these relatively intact ions and deliberately fragment an interesting ion in isolation, something neither Viking nor Curiosity could do. By analyzing the resulting puzzle pieces of this ion, it is possible to determine the chemical structure of the original molecule from the Martian sample and thereby identify what it is.
This will be the first time this laser technique has gone to Mars, but tests on Earth show it will work. The prototype detected traces of organic molecules even in the presence of more perchlorate than Phoenix found in Martian soil, Brinkerhoff says. And in Mars-like samples collected in Yellowstone National Park, detects lipids and other molecules that are more complex than those collected by previous Mars missions.
MOMA, like its predecessors, also has a high temperature ovens and scientists can still choose to use them instead of the laser to vaporize samples. If the laser shows hints of amino acids, for example, the oven option may provide information that the laser cannot. When in furnace mode, MOMA uses three chemical reagents that stabilize molecules to facilitate mass spectrometry. One of them, never before used on Mars, is there to distinguish between left and right amino acids, allowing it to prove living or non-living origins in a way that previous missions could not.
MOMA won’t be the last word on whether life once existed on Mars. Even the most tantalizing results will need to be confirmed by repeated experiments and lines of evidence from the rover’s other instruments, Vago says. Some confirmatory work may also be done through other missions or even someday from analysis of Mars samples returned to Earth. “We’re going to have to build a case, because otherwise no one will believe us,” Vago says.
The international team of scientists working on the mission knows what they need to build that case, but until the Rosalind Franklin Rover lands on the surface of the Red Planet, they can’t begin. All of these scientists shared the disappointment in March 2022 that the long-delayed mission was once again delayed.
But for Brinkerhoff, that disappointment is tempered with excitement: After all, the mission is still alive. “This thing is the best of all of us,” he says, “and just seeing it work on Mars will be career catharsis.”
Carmen Drall is a freelance journalist and editor based in Washington, DC. This article originally appeared in Knowable Magazine, an independent journalistic venture from Annual Reviews. Read the original here.