Mars wasn’t always the dry, dusty world we see today.
About 4 billion years ago, Mars had a thick blanket of air and a warmer climate.
Warm enough to have liquid water on its surface.
Scientists think a huge ocean once covered nearly a third of the planet — along with rivers, lakes, and maybe even rain.
Then everything changed.
Over hundreds of millions of years, Mars lost most of its air. Solar wind slowly stripped it away, because Mars didn’t have a strong enough magnetic shield to hold onto it.
Without that thick blanket of air to trap heat, the water froze, dried up, or sank underground.
What’s left is the cold, red desert we explore with rovers today.
It’s a haunting reminder of how fragile a planet’s ability to support life really is.
If Mars once had oceans… do you think it ever had life? 
