Part of Liquid State, an occasional series on our relationship with water.
Water was all around when John Moores was growing up in Newfoundland. It was part of the scenery and part of his identity. These days, water is still a big part of his life. The difference is that Dr. Moores now spends much of his time thinking about water that is millions of kilometres from home.
An assistant professor of space engineering at York University, Dr. Moores is a participating scientist with the Mars Science Laboratory, the $2.5-billion (U.S.) project that deposited NASA’s Curiosity rover into a Martian crater last summer and is yielding new insights into what once transpired there.
“Water is a big part of it,” Dr. Moores said in an interview with The Globe and Mail. “We really want to understand what the water story of Mars is: how it changed from being a warm and wet planet in the past to being the arid planet it is today, and whether or not it periodically comes back to life.”
The motivation is as big as it gets in science. Of all the questions humans have sought to answer about the cosmos, none are as potent as: “Are we alone?” After more than half a century of exploring the solar system, we still do not know if life, as a phenomenon, is unique to Earth, and what that implies about our chances of finding other civilizations some day among the stars.
For Curiosity – which landed a year ago on August 5 – the road to ET is a wet one.
In recent weeks, Curiosity’s explorations have literally shifted into high gear as it begins a series of long drives toward a mysterious mountain that promises the most complete record yet of the planet’s aqueous history.
Here on Earth, water is essential to biology. It is the universal solvent that, billions of years ago, allowed the chemical building blocks of life to interact and somehow assemble themselves into the first self-sustaining organisms. Ever since, evolution has driven life into a dizzying array of new and surprising forms – infinitely diverse, but inevitably dependent on water.
Scientists have known for years that there is water on Mars too, albeit mostly frozen solid at the poles or locked in subsurface permafrost. But there is also ample evidence that water flowed freely on Mars billions of years ago, raising the possibility that life may have once gained a foothold there.
Dr. Moores already has his own history with water on the red planet. While working on the Phoenix mission, which landed on the planet’s northern plain five years ago, he was among the first to detect fog on Mars – a fitting claim to fame for someone who hails from St. John’s.
These days, his work with Curiosity involves tracking the movement of water vapour through the thin Martian atmosphere in response to seasonal changes. With spring having just arrived at the rover’s location in Gale Crater on July 31, Dr. Moores expects to see more evidence of water overhead.
“It does start to pick up now that we’re moving into warmer temperatures in the Northern Hemisphere,” he said. For the rover, that still means daytime highs are below zero C, but as the Martian north pole is increasingly exposed to sunlight, the frozen water there evaporates directly into the atmosphere and forms clouds that migrate around the planet.
Getting a handle on this movement of water is important because water in the atmosphere interacts chemically with surface rocks and can skew measurements designed to reveal the much more ancient history of water – and potentially life – on Mars. Day by day, Dr. Moores and his colleagues watch how minute quantities of water are moving around in the Martian atmosphere, and in doing so help to decode a bigger story.
Ralf Gellert, a physicist at the University of Guelph, is working that story from the other side. He leads the rover’s alpha-particle-X-ray spectrometer (APXS), a device that measures the elemental composition of Martian rocks and can help identify minerals that formed in the presence of water billions of years ago.
As the creator of two similar instruments that landed with the Spirit and Opportunity rovers when they touched down in 2004, Dr. Gellert has spent nearly a decade absorbed in the daily business of exploring Mars in more than one location at a time.
What Curiosity has added to the picture has been “amazing,” Dr. Gellert said, with the new results clearly showing Mars was once far more habitable than it is today. While Opportunity found places where Mars was once likely covered with evaporating lakes of acidic water, Curiosity has tapped into an even older geologic era, perhaps 3.7 billion years ago, when at least some of the water on Mars was more like freshwater found on Earth today.