The News is that we have found our first possible candidate exoplanet that might house extrasolar life: Gliese 581g, known as Goldilocks. This is great news for those us who care. Why?
The clock is ticking.
All Our Eggs are in This One Basket.
We’ve all seen movies like Armageddon where an apocalyptic asteroid is headed for Earth. It’s not just pure fiction. An asteroid strike was responsible for the great dinosaur extinction, the end of a group of species that had dominated the planet for a hundred million years. A quick survey of meteor strikes in Earth’s history will show that it happens, sometimes catastrophically, and not always in the distant past.
The best way to improve the survival odds of the species is to get us off this planet and seed a few others. Even if we manage a zap-ray that will protect us from The Hammer of God, the Sun will die in another five billion years. While our species is honestly not likely to last that long (c.f. the film, Idiocracy), if we haven’t moved on by then it will surely all be over.
So where could we go?
If we can stay alive and technologically viable long enough to evade Lucifer’s Hammer, we’ll need other bases of operations. Terraforming the moons of our system’s gas giants might be an option. We’d still be in the same stellar back yard. Real safety is much improved if we spread ourselves across the stars, such as to Gliese 581, a possibly viable red dwarf 20 light years away.
That’s where Goldilocks comes in. It’s the first potentially Earth-like exoplanet we’ve found in the habitable zone of it’s star.
What’s it like?
We can’t tell yet, but we know that Goldilocks is in the range where water can be liquid. It has about three Earth-masses. We also know that it’s tide-locked, which means one side always faces Gliese 581, and the other side is in eternal darkness, much like our moon always faces its same side to the Earth.
What can we guess about Gliese 581g, or the Goldilocks planet, from that? We can guess anything we want, but it’s reasonable that there would be water on Goldilocks. We have three planets in our habitable zone — Venus, Earth, and Mars — and Earth is covered with water on more than 70% of its surface. Mars was thought to be dry for a long time, but ice has been found on at least one pole. It appears to be fairly plentiful about a meter beneath the surface elsewhere. Venus might once have been green like Earth. A runaway greenhouse effect turned it into an acid-raining hell hotter than my oven can get.
First, consider the gravity. Goldilocks is three Earth masses, but that doesn’t automatically mean it has three times the gravity. If Goldilocks’ mass is largely due to heavy metals like nickel and iron, then it might well have more then three times the surface gravity of Earth. If it has a large percentage of lighter materials it could be more tolerable.
Second, though there’s decent odds of liquid water, that doesn’t mean life has evolved there. If it did, it does not mean it would have to be based on the same chemistry and balance that stabilized our atmosphere at 21% oxygen. It certainly doesn’t mean there’s 70% nitrogen, though maybe something else could fill that atmospheric niche without killing us on our first breath. Unfortunately, Goldilocks’ orbit never goes between us and Gliese 581, so we can’t determine it’s chemical composition. It has enough mass to hold an atmosphere, but we have no way to prove one exists.
Third, since Goldilocks is tide-locked, there’s no day/night cycle. Gliese 581 doesn’t move in the sky unless you travel. Ecological niches would be stable in circular bands, only varying because of irregularities mountains and valleys and lakes, or mineral variations. There would be no seasons; summer is when the sunlight strikes most directly wherever you are, and it’s winter in the other hemisphere. Since Goldilocks is tidally locked to Gliese 581, summer is always on the part of the planet at high noon, and deepest winter is across from it at perpetual midnight.
One thing you could bet on, though. If there’s an atmosphere at all on Goldilocks, there’s weather, and which way would the wind blow? Always toward Gliese 581! Why? Because the solar heat would be warming the air on the sunward side of the planet, causing it to rise into the upper layers and be pushed aside by new wind rising behind it. On the dark side, all that heat would drain away, and it would sink toward the midnight pole, to rush across the ground toward the heat of the star again. With such a predictable weather pattern, the speed of the winds would likely build to scary intensities, depending on terrain, air density, and the amount of heat transferred. Keep in mind that almost no light reaches the surface of Venus’s greenhouse.
So why don’t we just go!
It’s not that easy. Gliese 581 is twenty light years away. That means that as of this writing, the light you’re seeing when you point a telescope at it came off the star in 1990.
We currently haven’t managed to mount a manned trip to Mars, our closest next door neighbor. Voyager 2, a simple unmanned probe, was launched August 20, 1977, and after over 12,000 days of travel is still less than 13 light hours from the sun. We’ve made a few advances in the last thirty-three years, but nothing that puts a significant dent in the twenty light years to Gliese 581g. It the rate of Voyager 2, it would take us well over a thousand years to get there. I don’t know about you, but that’s not a cruise I’d sign up to join.