Imagining Mars with Dr. Villanueva

December 24, 2015 

Carl Sagan once said, “Imagination will often carry us to worlds that never were, but without it, we go nowhere.” This sentiment is echoed by Geronimo Villanueva, who has a theory about why the Mars exploration program isn’t as far along as it could be.

“When the big Viking landers landed on Mars, they were looking for life. They had very simple experiments, and when they took their measurements, they didn’t detect life as we know it. So the public was like, “You know what? It’s a dead rock. What is the purpose? Let’s do something else.” And that killed the Mars exploration program for nearly 20 years,” said Dr. Villanueva in an interview with Heather D’Angelo from NOW.SPACE at the 18th Annual International Mars Society Convention in Washington, DC.

Dr. Villanueva, who is a planetary scientist at NASA Goddard Space Flight Center and the leader for Mars studies for the James Webb Space Telescope (JWST), believes the image of Mars as a “dead rock” has finally begun to fade from the public’s collective mind.

He credits this shift in perception to the groundbreaking discoveries made by NASA’s Mars Exploration Rovers, which drew a much different picture of the Red Planet than had ever been portrayed. The first rovers, Spirit and Opportunity, arrived separately on Mars in 2004. Spirit’s panoramic images depicted a rocky, sloping terrain of rippled dunes and vast plains, not unlike our own deserts here on Earth. But when one of the robot’s six wheels malfunctioned, the gouge left in the soil revealed silica-rich deposits, providing strong evidence of past water.

Not to be outdone, Spirit’s sister, Opportunity, identified rocks loaded with phyllosilicate clay minerals, which are known to form in relatively neutral pH water. This observation was later confirmed by the next rover, Curiosity, which found not only evidence of water but also the organics that make up the building blocks of life and the minerals that primitive microbes utilize for food.

The profound significance of these last discoveries compelled the principal investigator for the Curiosity mission, John P. Grotzinger, to declare, ”We have found a habitable environment that is so benign and supportive of life that probably—if this water was around and you had been on the planet, you would have been able to drink it.”

According to Villanueva, these discoveries have captivated the public’s imagination, inspiring a mental terraformation of the landscape from the cold, barren wasteland depicted in old science textbooks to a more Earth-like representation, where soft clouds drift across sunset-pink skies, and microbial life thrives in winding streambeds. He feels narratives like these are critical for galvanizing the public’s support of future Mars exploration missions.

“If you engage the imagination about Mars’ habitability, it makes people think, “We should go there!” he said. “We need more of those stories.”

In the past year, Villanueva has significantly contributed to a more comprehensive vision of ancient Mars by finding evidence that nearly half of its northern hemisphere was once covered by an ocean. This primitive body of water would have been approximately the same size as the Atlantic Ocean, with a maximum depth of one mile. At its greatest volume, it would have covered nearly 20% of the surface. While this is significantly less than the roughly 70% surface water on Earth, it would have been a large enough body of water to provide stability for life to take hold.

This valuation was made after Villanueva and his team spent six years measuring the distribution of two slightly different forms of water molecules in the Martian air from season to season. While the existence of two kinds of water may seem like an alien idea, its normalcy here on Earth allows scientists to understand Mars’ water. On both planets, there is the standard H20 water molecule, in addition to a “heavy” water molecule made from one oxygen, one hydrogen, and one heavy isotope of hydrogen, called deuterium.

“The ratio between these two types of water, standard and “heavy,” tells us a lot about evolutionary processes. It’s like a fingerprint or signature because it does not change over time. You can measure isotopic ratios across the solar system, from water in comets to meteorites, to Mars,” said Villanueva.

When his team did so for Mars, they were surprised to find a high ratio of “heavy” water to standard water in the current atmosphere—meaning high concentrations of the hydrogen isotope, deuterium. The large quantity of deuterium was used to infer how much standard water had been lost to space over billions of years. The scientists discovered that nearly 87% of Mars’ original water had disappeared.

Naturally, the next big questions to answer are: Where did the water come from, and where did it go?

As for the former, Villanueva explains, “We have water on Earth, but we don’t know where it came from. There are a few ideas of how that happened. For instance, initially, when the Earth was created, the weather percolated and formed the oceans. Another idea is that comets or meteorites, something external, delivered water. But the different hypotheses for water on our planet also apply to Mars.”

For the latter, scientists hypothesize that as the atmosphere on Mars thinned, the drop in pressure made it difficult for water to remain in its liquid state. The bulk of ocean water eventually escaped into space, while around 13% of it migrated northward to the poles and froze within the planet’s ice caps.

With so much water around for millions of years, it isn’t a stretch of the imagination to consider that life developed on Mars, much as it did here.

“4.5 billion years ago, the two planets were very similar in terms of habitability. They were both geologically active. Then you bring that water in, and you mix all these things—heat, temperature, rocks, water—and then you have a very interesting environment. It’s likely that if comets brought water, they also brought those building blocks of life, called organics. So if the building blocks for life came to our planet, then they must have also gone to Mars,” Dr. Villanueva said.

Villanueva and his colleagues hope to finally confirm the existence of Martian life, past or present, when ESA launches its ExoMars mission in January 2016. The mission consists of two parts: the Trace Gas Orbiter (TGO) and the Entry, Descent, and Landing Demonstrator Module (EDM, aka Schiaparelli). The Trace Gas Orbiter will be looking for the presence and location of gases such as methane in the Martian atmosphere, which is of particular interest to Villanueva.

In 2009, he and his NASA colleagues announced that they had observed and mapped multiple methane plumes in the atmosphere; however, much speculation surrounds whether they were caused by geological and/or biological processes. Villanueva thinks that ExoMars 2016 will provide the insights needed to confirm these claims.

“I’m excited about the ExoMars mission because it will clear up the cloud surrounding some of the debates about Mars. We’ve never before had the spacecraft to do those measurements. So we’ll finally be able to remove doubts about habitability, gas currents, organics. It’s a pretty important mission for Mars exploration,” he said.

If ExoMars 2016 finds evidence of life on Mars, it will complete the picture of Mars as a warmer, wetter, and thus, fertile planet—a sibling of sorts to Earth. This would have profound implications because if life has existed or does exist there, then it’s likely that life exists elsewhere in the universe.

Perhaps there are other habitable planets out there? If so, who knows what that life would look like on them? As the past has shown, the desire to answer these questions begins with our imaginations.