The living inhabitants of the soil and seas are well known to biologists. We have long studied their food chains, charted their migration, and speculated about their evolutionary origins. But a mile down an unused tunnel in the Beatrix mine in South Africa, Tullis C. Onstott, Professor of Geosciences at Princeton and author of Deep Life, is on a quest for mysterious bacteria and microbes that require neither oxygen nor sun to survive. When they open up an old valve, water full of microbes and even little worms flows—a discovery with stunning implications. The New York Times has chronicled Onstott’s research in a feature that asks, was there ever life on Mars? And could it still exist far below the surface? That organisms are nourished by our own earth’s core, thriving in darkness encased in hard rock provides major insights:
The same conditions almost certainly exist on Mars. Drill a hole there, drop these organisms in, and they might happily multiply, fueled by chemical reactions in the rocks and drips of water.
“As long as you can get below the ice, no problems,” Dr. Onstott said. “They just need a little bit of water.”
But if life that arose on the surface of Mars billions of years ago indeed migrated underground, how long could it have survived, and more to the point, how can it be found? Kenneth Chang writes:
If life is deep underground, robotic spacecraft would not find them easily. NASA’s InSight spacecraft, scheduled to launch in 2018, will carry an instrument that can burrow 16 feet into the ground, but it is essentially just a thermometer to measure the flow of heat to the surface. NASA’s next rover, launching in 2020, is largely a clone of Curiosity with different experiments. It will drill rock samples to be returned to Earth by a later mission, but those samples will be from rocks at the surface.
In the meantime, what can we learn deep in Earth’s mines? What do we know now about the energy required to sustain life underground? As Chang notes, if Beatrix is a guide, methane could be the answer:
As NASA’s Curiosity rover drove across Gale Crater a couple of years ago, it too detected a burp of methane that lasted a couple of months. But it has not detected any burps since.
Perhaps an underground population of methanogens and methanotrophs is creating, then destroying methane quickly, accounting for its sudden appearance and disappearance from the atmosphere. If Beatrix is a guide, the methane could be providing the energy for many other microbes.
Conventional wisdom is that Martian life, if it exists, would be limited to microbes. But that too is a guess. In the South African mine, the researchers also discovered a species of tiny worms eating the bacteria.
“It’s like Moby Dick in Lake Ontario,” Dr. Onstott said. “It was a big surprise to find something that big in a tiny fracture of a rock. The fact it would be down there in such a confined space slithering around is pretty amazing.”
A full account of Dr. Onstott’s work appears in the New York Times feature, Visions of Life on Mars in Earth’s Depths.
Read more about Deep Life: The Hunt for the Hidden Biology of Earth, Mars, and Beyond here.