My Favorite Fact About Earth

Hello, friends!  I’m going through some life changes right now, which leaves me precious little time for writing.  But I still want to write something, so during this time I’m just writing this series on my #1 favorite facts about each planet of the Solar System.  Today, I’d like to share my #1 favorite fact about Earth.

I love bringing this fact out at parties.  It’s a great conversation starter.  In 1990, NASA discovered life on Earth.

Okay, so here’s the story.  Prior to 1990, NASA sent all these missions out into space, hoping to find life.  Finding life should be easy, right?  And yet, they found nothing.  It was enough to make some scientists ask: “Are… are we doing something wrong?”  So at the suggestion of one of those scientists (Carl Sagan), NASA turned all the instruments of one of their space probes toward Earth, just to check and make sure those instruments could detect life on a planet where life was already known to exist.

And it worked!  Based solely on the data from that one space probe, NASA confirmed that there is life on Earth.  There were several compelling lines of evidence.  Here’s just one example.  NASA detected traces of methane in Earth’s atmosphere.  That, by itself, proves absolutely nothing.  NASA also detected oxygen in Earth’s atmosphere.  Atmospheric oxygen, by itself, also doesn’t mean much.  But the combination of oxygen and methane in the same planet’s atmosphere?  That’s odd.  That’s very, very strange.  It’s hard to explain how a planet ends up with an atmosphere like that, unless it’s due to biological activity.

Someday, astronomers may discover life on a distant exoplanet (a planet orbiting a star other than our Sun).  If/when that happens, one of the first signs of alien life will probably be a weird mix of chemicals in the exoplanet’s atmosphere.  It doesn’t have to be oxygen and methane.  It doesn’t have to be any of the chemicals found in Earth’s atmosphere, necessarily.  It just has to be a mix of chemicals that don’t make chemical sense together.  Searching for weird mixtures of atmospheric chemicals is one of the easiest ways to detect life on a planet.  We know, because that was one of the ways NASA detected life on Earth in 1990.

Thank you, friends, for reading.  We’ll continue this series later this week with my #1 favorite fact about Mars.