Part 1 of 5 · freeIntroduction
For decades, scientists have searched Mars for signs of past life. All known life needs water, yet the Martian surface today is cold and extremely dry. Mars was not always like this, though: rovers, the wheeled robots that explore its ground, have found rocks and minerals that only form in the presence of liquid water.
Seen from above, the landscape confirms it: ancient river valleys, deltas, dried-up lakebeds. Many of these features are more than 3 billion years old. NASA has even found traces of gigantic floods about 3.5 billion years ago. So water once flowed on Mars. The mystery remains: how did a wet planet turn into this desert?
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- 2A thick atmosphere was needed
- 3Mars lost its atmosphere
- 4Not all the water left
- 5Dry, but not waterless
Open-book quiz8 questions whose answers are in the text.
Glossary6 terms explained in a tap.
30 languagesThe same course, from French to Japanese.
