The Life of Super-Earths by Dimitar Sasselov

Author:Dimitar Sasselov
Language: eng
Format: epub, mobi
Publisher: Basic Books
Published: 2012-01-24T16:00:00+00:00

CHAPTER NINE

LIFE AS A PLANETARY PHENOMENON

Half a day’s sail northwest of the Cape of Good Hope lies Cape Town, South Africa. Even today, the city feels like an outpost, a cozy yet uneasy harbor at the edge of the world. After all, there is, to human eyes, nothing south of there but cold and ice, a frigid southern ocean encircling the least hospitable landmass on Earth.

There, in the shadow of exotic Table Mountain, in November 1873 an unusually outfitted British ship, HMS Challenger, was being readied for a grueling journey to the icy shores of Antarctica, then on to Australia and around the world. Forty years after the famous trip of the HMS Beagle with Charles Darwin onboard, HMS Challenger was on a four-year voyage to explore a new frontier—the depths of the world oceans.1 HMS Challenger had a complement of six scientists in its crew and a deck loaded with curious instruments: for measuring oceanic temperatures, depths, and currents; for taking deep-ocean samples; and for capturing living specimens of whatever creatures might call the strange place home.2

The results astounded laypeople and scientists alike. From the total darkness and tremendous pressure found eight or more kilometers below the surface, HMS Challenger collected 600 cases of specimens. The rich harvest proved that the vast underwater landscape of the oceans is not a desert. Life was everywhere on the surface of our planet.

More recently, research in the last twenty years has led to two more astonishing realizations. First, rather than simply providing a home for life, planet Earth has been thoroughly transformed by life, which has accompanied it almost since its formation 4.5 billion years ago. What’s more, as fragile as life may appear to be, clinging to the surface of a small planet that is subject to violent cosmic events, what we have learned has led us to conclude that life on Earth is virtually indestructible. The evidence suggests that it has been that way for a very long time, perhaps 3 billion years.3 Destroying all living things on Earth, including spores and complex biomolecules, would take nothing short of melting and vaporizing the planet in the sterile interior of the Sun. Destroying life would also require annihilating all the spacecraft in Earth orbit, as well as the other places we’ve sent space probes. Though unlikely, the possibility that we’ve colonized Mars with some microbes, for example, is not that far-fetched; many extremely resilient microbes have been discovered in the past thirty years, and some—such as Deinococcus radiodurans—are hardy enough to survive the trip to Mars.4 Real space travelers!

The secret behind the indestructibility of the Earth biosphere lies in the sheer diversity and inventiveness of the organisms that have always ruled “our” planet—the microbes. The hardiest among them are called extremophiles, meaning that they inhabit extreme environments. Some are able to withstand 250°F (122°C) in hot springs and in ocean floor “black smokers”—hot volcanic vents. Others survive high pressure levels, for example, in the sterilizing high pressure vats for orange juice5 or in the natural habitat of the Marianas trench in the Pacific Ocean at 800 atmospheres.

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