In a previous post I wrote about how we discovered the age of the Earth, and I mentioned that our planet formed at the same time as the other rocky bodies in our Solar System.
I didn’t say HOW this happened though. So now I will.
Astrobiology don't you know… sort of
In 1650 the Archbishop James Ussher announced that the Earth was thousands of years old.
Almost six thousand years old in fact. He had discovered that the world had been created on the 23rd of October 4004 BC. At lunchtime.
This was a pretty momentous conclusion. Not only had Ussher calculated the age of our world to a superhuman degree of precision, he was also lending credence to the idea that the Earth had a beginning (many cultures believed the Earth has always existed, and always will) and that it was pretty damn old, 6,000 years-worth of old.
Today, most people are comfortable with the idea that the Earth hasn’t existed in perpetuity, and most people are OK with the fact that the Earth is billions of years old. But this is a pretty recent mindset. Up until about one hundred years ago, no one really had any idea how old the Earth was.
Here’s what happened…
Heard of the Goldilocks zone?
It’s the idea that an area of space around a star will be at the right temperature for life to exist. Not too hot, not too cold, hence Goldilocks.
It’s a bit like standing around a campfire on a very cold night. Stand too far away and you freeze, stand too close and you catch on fire and burn to death.
It’s the same with planets orbiting stars too, if they’re too far away then water freezes and life can’t emerge, and if they orbit too close the planet is roasting hot and nothing can live.
It gets a bit more complex than this though, but complex in a fun way. Oh and its also got some pretty big implications for the search for extraterrestrial life…
In this series of posts I’ve looked at planetary bodies in our Solar System that could support life, from the moons of Saturn and Jupiter, to the cloud layers of Jupiter itself, to the ephemeral-once-jungles of Venus, I’ve even looked at Earth itself.
Now one of my favourites, Mars, the Red Planet.
I’ve been a bit scared about doing this post, but thought I should, as I’ve done posts already on what a solar system is, and what galaxies are, and the Universe is next up in the cosmic scale, so it was only a matter of time until the nagging-voice from somewhere in my brain advocating ascetic completeness won the day and I sat down to do this.
I’ve been a bit scared because it’s a pretty big question, what is the Universe? And I’m primarily a student of geology and biology, so who am I to answer such a question? I’ll give it a stab though…
In previous posts I’ve looked at some likely, and some less likely, candidates for planets or moons in our solar system that could harbour life, including Jupiter, three of it’s moons, two of Saturn’s moons, and Mars and Venus.
Now its time for Earth. Yep, you read right.
In 1990 NASA used the Galileo spacecraft to look for life on Earth. Why bother you scream, whilst hurling your cup of tea violently against the wall? Well, NASA did it to test how well spacecraft like Galileo can find life on planets and moons from space. Call it a proof of concept, if NASA can find life on Earth, then at least they know the tech works, and hopefully won’t miss signs of life on other planets.
Here’s what they found on Earth:
This time we’re moving nearer to home, to the planet closest to our own, Venus, the second rock from the Sun.