At the end of 2011 astronomers announced the discovery of the most likely candidate yet for another planet on which human beings might survive if push comes to shove. But what’s wrong with this one?
The Kepler spacecraft is an American space observatory. It was named in honour of the 17th-century German mathematician and astronomer Johannes Kepler and launched in March 2009. Its mission is to survey our region of the Milky Way to discover Earth-size planets in or near the habitable zone (where liquid water could exist on a planet’s surface and where the temperature is neither too hot nor too cold to support life). Kepler’s only instrument is a photometer that monitors the brightness of over 145,000 stars in a fixed field of view. The data is transmitted to Earth and analyzed to detect periodic dimming caused by extrasolar planets that cross in front of their host star.
Astronomers have now confirmed the existence of an Earth-like planet in the habitable zone around a star not unlike our own. The planet, Kepler 22-b is about 2.4 times the size of Earth and has a temperature of about 22C. It is the closest confirmed planet yet to one like ours although scientists do not yet know if it is rock, gas or liquid. Kepler 22-b lies a tad closer to its sun than the Earth is to our Sun, and its year takes about 290 days. The planet’s host star puts out about 25% less light, keeping the planet at a temperature that would support the existence of liquid water. Unfortunately, Kepler 22-b lies 600 light-years away (that’s 600 x 9,460,730,472,580 kilometres) and is unreachable using contemporary technology.
Peering through the other end of the telescope, we can be reasonably sure that if there were a highly advanced civilization out there, it would have been here by now. The logical conclusion is that spaceship Earth is on its own and we human beings have to fend for ourselves. That notion is especially poignant if we take into account the increasing likelihood of being struck by one of the great lumps of rock whizzing around the universe.
Earth has been hit by asteroids many times in its history – the best known example being the one that created the Chicxulub crater in the Gulf of Mexico and probably contributed to the extinction of the dinosaurs at the end of the Cretaceous Period 65 million years ago. A more recent but less devastating example, called the Tunguska event, occurred in 1908, when a meteor or comet exploded over the wilderness of Siberia, levelling trees for miles around.
There are high odds that the Earth will be hit by another asteroid sooner rather than later. In 1992 astronomers discovered the Kuiper Belt, a region of asteroids and comets beginning near the orbit of Neptune and extending for an immense distance outward. At least 1,000 rocks have already been observed there. They are much bigger than the one that dispatched the dinosaurs.
Natural catastrophes apart, human beings are quite capable of wrecking planet Earth for themselves. Unregulated exploitation of natural resources has led to irreparable ecological damage; global warming exacerbated by human activities such as burning fossil fuels and deforestation has led to famine, drought, and displacement of people; and global militarization has led to greater inequality, poverty, and bitter conflict.
Long before we work out how to reach the nearest life-sustaining planet, the Earth will become uninhabitable. We owe it to ourselves to care because clearly no deus ex machina is going to save us. As French biologist and Nobel Prize winner Jacques Monod wrote in Chance and Necessity (1971): “Man knows at last that he is alone in the indifferent immensity of the universe, whence he has emerged by chance. His duty, like his fate, is written nowhere. The choice of making his life a heaven or a hell is his alone.”
So, a far from original New Year’s resolution for humanity: “We are on our own. Let’s mend planet Earth while we can!”