Rock and Rovers
Scientists are studying Ontario limestone to learn about extraterrestrial life
Scientists are studying Ontario limestone to learn about extraterrestrial life
Red lake, a small municipality northwest of Thunder Bay, is one of the most isolated tourist spots in Ontario. Each year, hundreds of wealthy visitors, mostly American, make the trek north to the region’s cluster of lakes to catch prize-worthy pike, trout, and walleye. One early morning last August, Stefan Lalonde, a scientist who had just flown in from France, joined the fishermen among the towering pine trees. Armed with a drill, a magnet, and a small bottle of hydrochloric acid, he had one particular prize in mind: rocks. Those rocks could eventually lead other scientists to extraterrestrial life.
Lalonde, who studied geomicrobiology at the University of Alberta and now works with the European Institute for Marine Studies, weaved his rented motorboat through the lake. Approximately thirty kilometres away from the town’s main dock, he found what he was looking for, just above the surface of the water. At first, the limestone seemed unexceptional: rigid and grey. But when Lalonde placed a single drop of acid on the rock, it reacted with the carbon dioxide inside and fizzed up like a baking-soda-and-vinegar volcano. With a small pick and hammer, he chiselled off samples of the rock, some of which he would transport back to his lab in Brest, France, where they would be cut, crushed, and analyzed to understand Earth’s early biosphere. Astronomers could then use that information to predict what kinds of planets can support life and then search the universe to find them.
Science-fiction movies would have us believe that space exploration features people in spacesuits and high-tech rovers in far-off places. But our quest to understand everything outside of Earth’s atmosphere is usually less glamorous — a collaboration between scientists across the world from different disciplines, working together over decades on the most specialized of problems (calculating the amount of gas in a rock sample, for example, or writing the code to manoeuvre radio telescopes). So if we do encounter extraterrestrial beings, it likely won’t be because we’ve landed on their doorsteps — or they’ve landed here — but because a lab discovery, years or decades in the making, led us to their planet.
The more scientists know about how life evolved on Earth, the better they’re able to identify the conditions that could help it evolve elsewhere. With the work of scientists like Lalonde, the study of our own planet begins to have much larger implications. As humanity reckons with the realities of climate change — the fragility of Earth’s atmosphere and its importance to our very survival — understanding what conditions are needed to sustain life is becoming increasingly important. Modern-day geology could also help scientists answer fundamental questions about our own biological existence: How did life begin, and what conditions are needed to sustain it here and on other planets? “When you buy a house, you ask questions about when it was built and who lived there before. The Earth is the same,” says Philip Fralick, a geology professor at Lakehead University in Thunder Bay, Ontario. “It’s our home, and understanding how it evolved gives us insight into how we got to be here right now.”
During part of the Precambrian era — the earliest and longest part of Earth’s history — more than 500 million years ago, the portion of land that would eventually become
Ontario was in the centre of a giant supercontinent. The world was unrecognizable: there were no trees, and many lakes were extremely salty. As Earth got warmer, that water evaporated. It left behind a cocktail of chemicals — including calcium sulphate (which is often used for drywall and bone grafts) and bicarbonate — that formed limestone and imprinted it with the equivalent of atmospheric DNA . As the world morphed into something that more closely resembled a modern-day map, those samples were preserved just below the surface of the earth.
Rocks function as time capsules: they record traces of the atmosphere and protect them for billions of years. Samples of limestone hold clues about the earliest days of the planet, long before mammals and vegetation existed. Unlike in South Africa and western Australia, limestone in the Canadian Shield was preserved by glaciers, and some of the continent’s oldest specimens remain near the earth’s surface — which is why Canada is one of the richest sources of ancient rocks in the world. The limestone Lalonde studies is about 3 billion years old. Back then, the sun was around 25 percent dimmer. Researchers used to believe that Earth was a giant ball of ice during this period. But limestone, which needs water to form, tells us something different: there must have been oceans and lakes at the time. Apart from the direct heat of the sun, the only way to sustain a temperature warm enough to keep water from freezing is with carbon dioxide, which traps the sun’s heat, so scientists know there was far more CO2 in the atmosphere than there is today.
Elizabeth C. Turner, a geology professor and researcher at Laurentian University, in Sudbury, Ontario, says Earth’s biological evolution can be understood as a one-way arrow: it’s constantly moving forward, and every point in its history has been different. “If you travelled back to nearly any part of the past, the air would be unbreathable and you’d die instantly,” she says. The conditions necessary to host life elsewhere likely won’t resemble those of modern-day Earth but, perhaps, those of Earth as it was billions of years ago.
Piecing together the biological history of Earth might also require an understanding of how much oxygen was in the atmosphere billions of years ago, because most cells need it to survive. This past summer, Canadian and American researchers published the results of analyses of rock samples extracted from an evaporated lake near Thunder Bay. Their research suggested that, during the latter part of the Precambrian era, 1.4 billion years ago, the atmosphere had significantly lower oxygen levels than it does today — conditions that scientists didn’t think could support the life that existed at the time. “What we now know about the Earth paints a picture of a complete alien planet,” says Peter Crockford, the lead author on the project.
A glaring question remains: “whether microorganisms produced the conditions for modern life to thrive” — that is, bacteria raised the oxygen level of the atmosphere, thus setting the stage for the first animals to evolve — “or whether early animals themselves changed the environment and allowed oxygen levels to rise.” What came first, higher oxygen levels or complex life capable of evolution?
Nasa, with an annual budget of $21 billion (US), has funded some of the most significant projects in human history. The Cassini spacecraft left Earth in 1997 to investigate Saturn’s rings. More recently, the New Horizons spacecraft reached Pluto, one of the farthest corners of our solar system, in 2015, and the beloved Opportunity Mars rover spent fifteen years exploring the red planet. These efforts have expanded our understanding of the universe and the planets around us, opening doors to new realms of research — and to possible encounters. But, to date, explorers have found no evidence of extraterrestrial life, in part because they weren’t always sure where to look or what to look for.
Comparatively, spending on geological research is low (Lalonde’s annual trips to northern Ontario, for example, are part of a $2.6 million research project funded by the European Research Council). But geological research is also exceptionally insightful. Fralick, the geologist at
Lakehead, worked on Crockford’s project and has collaborated with NASA on how to detect life on other planets. Mars, he says, might be the most likely location for extraterrestrial life. Three and a half billion years ago, the atmospheric conditions on Mars were similar to those on Earth at the time. It was a warm planet with oceans, seasons, and clouds. As life developed here, there’s a reasonable chance it also developed there, says Fralick. But, because Mars is half the size of Earth, there is less gravity, and the planet gradually leaked its atmosphere into space — like a deflating balloon. The water vapour escaped, the soils turned red, and the oceans dried up, likely wiping out any trace of life that may have existed above the surface of the planet. “There’s a chance that there’s still life below the surface, though,” Fralick says.
In 2020, when NASA sends its next rover to Mars — with cameras, sensors, and a drill — it will be looking for signs of microbial organisms or ancient bacteria in its rocks. Those organisms are likely the same kind that dominated Earth for the majority of its history and eventually evolved to form more complex structures, like trees and animals, including us.
While it’s compelling to believe that we might one day discover life in extraterrestrial rocks, there’s also a more immediate application for this research: appreciating our own planet. Knowledge about the conditions and histories of other worlds — such as Mars and its deflated atmosphere — might also help us understand Earth. And, when we start to think of our planet in the same way we study an alien one, we begin to allow for a timeline that is not in decades or centuries but in billions of years. We begin to understand the interconnectivity of elements — of the atmosphere, the oceans, and greenhouse gases, for example — and how crucial their balance might be. We become more sensitive to the urgency of problems today, knowing that even a minute change in atmosphere might mean the difference between the evolution of life and the loss of life as we know it.