What do you think?
Rate this book


288 pages, Hardcover
First published February 7, 2019
"Scientists believe that Venus once had a lot of water in its oceans, but lost it over time, and perhaps from its oceans as recently as a billion years ago. The reason we can tell this is from the isotopic composition of hydrogen measured in its atmosphere by spacecraft. Now, hydrogen has two flavors of isotopes. Whereas most hydrogen atoms are just a single proton in the nucleus, some, a small fraction, are what we call deuterium, that have a proton and a neutron, so they weigh twice as much as the regular hydrogen. What happens when you have evaporation of water from a planet, or the atmosphere, is that the water molecules that contain hydrogen are much lighter than the water molecules that contain deuterium, so they evaporate more easily, and can be lost more easily. So, over time, as you evaporate water, more deuterium bearing molecules stay behind relative to the regular ones, and you build up a big deuterium to normal hydrogen ratio. And by back-calculating from the measured ratio today, we can figure out how much water has been lost over billions of years of evolution, and it's quite a lot."

Seven Minutes of Terror - in the words of Curiosity mission's Leader Allen Chen
Things are looking good. Coming up on entry
Vehicle reports entry interface
We're beginning to feel the atmosphere as we go in here
Alright, it is reporting that we are seeing Gs on the order of 11 or 12 Earth Gs
Bank reversal 2 is starting
We are now getting telemetry from Odyssey
We should have parachute deploy around Mach 1.7
Parachute has deployed
We are declining
Heat shield has separated, we are locked on the ground
We're down to 90 meters per second at an altitude of 6.5 kilometers and descending
Standing by for backshell separation
We are in powered flight
We are at altitude 1 kilometer and descending
Standing by for sky crane
Sky crane is starting
Signal from Odyssey remains strong
Touchdown confirmed! We're safe on Mars!
(cheering, applause)
We got thumbnails. It's a wheel! It's a wheel!
