Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
From a “watery past” to water today!
“If you look at the field of robotics today, you can say robots have been in the deepest oceans, they’ve been to Mars, you know? They’ve been all these places, but they’re just now starting to come into your living room. Your living room is the final frontier for robots.” –Cynthia Breazeal
Before we ever landed on Mars, there was evidence of water on its surface.
Frost, icecaps and clouds are some of the watery features that can be seen from a great distance on Mars. Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA).
Seasonal icecaps, transient clouds and frozen lakes are all abundant.
Seasonal frozen lakes appear throughout Mars, showing evidence of (not liquid) water on the surface. Image credit: ESA/DLR/FU Berlin (G. Neukum).
From orbiters, we could see what looked like a large number of dried-up riverbeds.
Oxbow bends only occur in the final stages of a slowly flowing river’s life, and this one is found on Mars. Image credit: NASA / Mars Global Surveyor.
Many of these contained oxbow bends, while others contained flowing features similar to what we see arising from mountaintops here on Earth.
These tendrils are evidence of water flowing down a slope and into a massive river. Image credit: NASA / JPL-Caltech / University of Arizona, Mars Odyssey / THEMIS.
There are canyons that show evidence of formation from water-based erosion, akin to the canyons on our own world.
The canyon shown to the left reveals similar structures to dried-up rivers here on Earth. Image credit: ESA/DLR/FU Berlin (G. Neukum).
From the surface itself, layers of sedimentary rock show further support for a watery past.
Sedimentary rock structures like this require water to make the proper deposits. Image credit: NASA/JPL-Caltech/MSSS, Mars Curiosity Rover.
By scraping the dirt on the martian surface, water-ice was revealed, which then sublimated.
The “holy cow” mosaic of the Mars Phoenix mission, with revealed water-ice clearly visible underneath the lander’s legs. Image credit: NASA / JPL / University of Arizona / Max Planck Institute / Spaceflight / Marco Di Lorenzo, Kenneth Kremer / Phoenix Lander.
Hematite spherules, known as “Martian blueberries,” provided strong indirect evidence of water.
Called Martian “blueberries” because of their color, these Opportunity-discovered spheres provide evidence for a watery past. Image credit: NASA/JPL/Cornell/USGS, Mars Opportunity Rover.
As water diffuses through the surface rock, minerals precipitate out of solution and form erosion-resistant spheres: geologically forming concretions.
Hematite spherules are found both on the surface and embedded in the surface rock, pointing to a watery origin. Image credit: NASA/JPL/Cornell/USGS, Mars Opportunity Rover.
But by far the strongest evidence comes from the recurring slope lineae.
Running down mountainsides and inside crater walls, thin, growing gullies can be found. Image credit: NASA/JPL-Caltech/Univ. of Arizona via Getty Images.
These “gullies” are seen to be actively growing, but not from landslides.
Recurring slope lineae on the Martian surface. Image credit: NASA/JPL-Caltech/Univ. of Arizona via Reuters.
Our orbiters show these lineae have perchlorate salt deposits inside.
These gully-like features grow in extent over time. Image credit: NASA/JPL-Caltech/Univ. of Arizona / Mars Reconnaissance Orbiter.
As liquid water dissolves the salts and flows, it sublimates/evaporates, leaving the deposits behind.
A color-enhanced view inside Newton Crater, showing the recurring slope lineae. Image credit: NASA/JPL-Caltech/Univ. of Arizona / Mars Reconnaissance Orbiter.
Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images, video and no more than 200 words.
