Looking for clues for past life on Mars

NASA's Curiosity Mars. Credits: NASA/JPL-Caltech/MSSS

On August 6, 2012, the NASA Curiosity rover landed on Mars at the base of Mount Sharp, a mountain the size of Kilimanjaro (~19,000 feet) in the middle of Gale Crater. Nina Lanza, space scientist at the Los Alamos National Laboratory, remembers the day well. As part of the team that built ChemCam, one of the ten instruments on the rover, she spent three months at the Jet Propulsion Laboratory in California, living on “Mars time” to follow Curiosity’s first “steps.”

ChemCam stands for “chemistry camera” and comprises a laser-induced breakdown spectroscopy (LIBS) instrument and a Remote Micro Imager (RMI). It was built at the Los Alamos National Laboratory in collaboration with the French space agency CNES. Nina Lanza and postdoctoral fellow Patrick Gasda are two of the Los Alamos scientists who work on the instrument.

“We get to shoot a laser on Mars for a living,” Lanza says, grinning.

And the laser on ChemCam is extremely powerful. When focused on a target, it vaporizes a small amount of material by heating Martian rocks to a temperature that’s roughly equivalent to that of the surface of the sun. “When we fire at a nearby target,” Gasda explains, “the elements get excited and, as they come down from that excited state, they emit light.”

By looking at the light emitted by the target, scientists can analyze the composition of rocks and soils on Mars. Previous Mars missions have found ice in the near-surface at high latitudes, begging the question: was there ever water on other parts of Mars at some point? And if there was—does that mean there could have been life, too?

With the very first laser shots from ChemCam, the answer was a definitive yes. “ChemCam discovered that all Martian dust is hydrated,” Lanza explains. “Given how dusty Mars is, this means that water is everywhere on the planet. We also found evidence that water was flowing in Mars’s past.”

“Gale Crater was filled with water,” Gasda adds. “From the sequence of sedimentary rocks we know of flowing streams in the crater that converged to a large body of still water that likely lasted for millions of years.”

“Curiosity gave us a picture of Gale Crater as an extremely habitable system,” Lanza continues. “We know that on Earth systems like this, with long-lasting neutral pH waters, would definitely support life.”

But how do you go about finding evidence for life? You search for clues, in other words, unique markers that identify biological activity.

“A potential marker could be manganese minerals,” Lanza says. In 2016 Curiosity found rocks rich in manganese-oxides at a location called Kimberley. “Manganese deposits in the terrestrial geological record mark the shift to higher concentrations of atmospheric oxygen due to the emergence of photosynthesis. This means that there could have been more oxygen in the Martian atmosphere in the past.”

Water. Oxygen. What about other building blocks of life? How do we look for those?

“Nucleic and amino acids have been found in space,” Gasda tells me. “However, ribose—the ‘R’ in RNA, one of the first building blocks of life—and other sugars have never been found in space because they are too unstable. In order to have life, you need molecules that stabilize these sugars in water. Borates are particularly promising molecules for stabilizing sugars [1].”

Boron is highly soluble in water. In 2013 researchers from the University of Hawaii found boron in a meteorite from Mars [2]. That’s when Gasda became interested in this quest. “Once we knew that Gale Crater had once hosted a large body of water, it was natural to search for boron in those sediments.”

ChemCam did indeed find boron on Mars in 2016. Together with the manganese oxides, this is still not sufficient evidence for life on Mars, but it shows that some of the raw ingredients were present. The scientists are primed to keep looking. Curiosity has been on Mars almost five years (or 1660 sols), and its data is helping researchers fine-tune the instruments for the next Mars rover, provisionally named Mars 2020, to be launched in July 2020.

“We need to look for biosignatures,” Lanza says. “And we may not find them. But if we don’t, to me, the most striking question would be: what if there were indeed all the ingredients for life on Mars, yet life never happened? What made Earth so unique that life could happen here but nowhere else?”

Gasda nods. “And if we are indeed unique, shouldn’t this make us feel more special, and make us more cautious about the way we treat our planet and our biodiversity?”

I mention the current political climate, with the planned budget cuts to scientific research, and the appalling denial of any intervention to curb global warming.

“These cuts to basic research are disheartening,” Lanza says. “People often think of NASA research as esoteric and out of touch. And yet almost everyone has GPS technology on their smart phones today, something we owe to space research. Take the electron as another example. I’m sure people in the nineteenth century found J. J. Thomson’s research on the electron to be highly academic, with few practical applications. Yet without his discovery we wouldn’t have electricity, and our lives today would be fundamentally different.”

“The best measure for progress,” Lanza concludes, “is when you can’t imagine the knowledge you are going to gain. Let the science surprise you.”

Nina Lanza is a staff scientist, and Patrick Gasda is a postdoctoral research fellow, both in the Space and Remote Sensing group at the Los Alamos National Laboratory. They are both on the science team for the Curiosity Mars rover mission. The opinions expressed here are their own and not their employer’s. Both will be speaking at the March for Science in Santa Fe, New Mexico, on April 22nd.

[1] Ricardo, A. (2004). Borate Minerals Stabilize Ribose Science, 303 (5655), 196-196 DOI: 10.1126/science.1092464

[2] Stephenson, J., Hallis, L., Nagashima, K., & Freeland, S. (2013). Boron Enrichment in Martian Clay PLoS ONE, 8 (6) DOI: 10.1371/journal.pone.0064624

What if black holes were not... holes? A Los Alamos physicist explains his alternative theory behind these mysterious objects.

© Elena E. Giorgi

The concept of a “black hole” — a celestial body so dense and massive that not even light can escape its gravitational field — dates back to the 18th century, with the theoretical work of Pierre-Simon Laplace and John Michell. But it wasn’t until the early 20th century that these mysterious dark objects were first described mathematically by German physicist Karl Schwarzschild. Schwarzschild’s work predicted the existence of a finite distance around the black hole (called the “event horizon”) from which light cannot escape.

Emil Mottola, a physicist in the Theoretical Division at Los Alamos National Laboratory, laughs as he explains this bit of history behind black holes. “Would black holes have captured the popular imagination if they were still known as Schwarzschild’s solution?” he quips. Mottola has a point. The name “black hole” was coined by the American physicist John Wheeler in the 1960s, when these objects became the subject of serious study and first entered the popular vocabulary.

“And then of course, Stephen Hawking made black holes very popular with his own research and theory of black hole radiation,” Mottola adds. “To this day,” he explains, “black holes are far from being understood, and science fiction may have taken over from science fact. We can’t answer many of the most important questions without knowing what the internal states of a black hole are, but no one has ever been inside a black hole, so no one actually knows what is inside.”

One particularly vexing feature of black holes is the so-called “information paradox.” In 1974, Stephen Hawking theorized that black holes emit small amounts of radiation (called Hawking radiation). However, if this is true, black holes should eventually evaporate due to the loss of mass, leaving no way—not even in principle—to recover the information that was originally enclosed in it. This question alone has generated hundreds of research papers with still no completely satisfactory resolution.

In 2001, Mottola and his colleague Pawel O. Mazur proposed an alternative to Hawking’s black hole theory that eliminates the paradox. “Think of a black hole as having a physical surface,” Mottola says. He imagines this surface to be much like a soap bubble that bends and fluctuates in space.
“Our idea is that quantum effects build up right at the event horizon (the bubble’s surface), leading to a phase transition. This in turn creates a gravitational repulsive force inside the “bubble” that prevents the surface from collapsing. This repulsive force is the same ‘dark energy’ force believed to cause the expansion of the universe. We call these objects Gravitational Condensate Stars or ‘Gravastars’— celestial objects that would be compact, cold and dark, and look to astrophysicists just like ‘black holes,’ although they are not ‘holes’ at all. Our hypothesis does not contradict the conservation of information because there is no infinite crushing of space and time inside a Gravastar, and information is never destroyed.”

According to Mottola, the mathematical equations Hawking used to describe the temperature of a black hole are in reality describing the surface tension of a Gravastar. “If we assume that black holes have a temperature, then they need to have an enormous entropy too, but we can’t easily explain that enormous black hole entropy. In our theory, black holes don’t have a temperature, they have surface tension, like soap bubbles. In 2015 we showed that this possibility of a surface and surface tension was already inherent in Schwarzschild’s original formulation of black hole interiors in 1916, and so is consistent with both Einstein’s General Relativity and Quantum Mechanics.”

As I look over my notes, I pose Dr. Mottola one final question: “Is there any way to find out who’s right, you or Stephen Hawking?”

He smiles because he knows that whatever Hawking says these days carries a lot of weight, including when he proposes that black holes could be mysterious portals to other universes.
“I believe we may well find out the answer in the next five to ten years,” Mottola says. “If ‘black holes’ actually are Gravastars with a surface, their surface oscillations would cause them to emit gravitational waves at certain frequencies, which is a substantially different signal than that expected from the black holes that Hawking and colleagues theorize. LIGO directly detected gravitational waves for the first time in 2015, so we have just entered a new era of gravitational wave astronomy. In a few years, we may have enough data from the gravitational waves detected by LIGO and its sister observatories to be able to resolve the conundrum.”

Needless to say, the Los Alamos scientist is very excited at that prospect.

References
[1] Mazur, P., & Mottola, E. (2004). Gravitational vacuum condensate stars Proceedings of the National Academy of Sciences, 101 (26), 9545-9550 DOI: 10.1073/pnas.0402717101

[2] Emil Mottola (2010). New Horizons in Gravity: The Trace Anomaly, Dark Energy and Condensate
Stars Acta Physica Polonica B (2010) Vol.41, iss.9, p.2031-2162 arXiv: 1008.5006v1

[3] Mazur, P., & Mottola, E. (2015). Surface tension and negative pressure interior of a non-singular ‘black hole’ Classical and Quantum Gravity, 32 (21) DOI: 10.1088/0264-9381/32/21/215024