# Earth has a twin where Mars is-past and current natural history?

**URL:** <https://boards.straightdope.com/t/earth-has-a-twin-where-mars-is-past-and-current-natural-history/709085>\
**Category:** Factual Questions\
**Created:** [January 6, 2015, 1:34am UTC](https://boards.straightdope.com/t/earth-has-a-twin-where-mars-is-past-and-current-natural-history/709085 "2015-01-06T01:34:02Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\
**Post date:** [January 6, 2015, 1:34am UTC](https://boards.straightdope.com/t/earth-has-a-twin-where-mars-is-past-and-current-natural-history/709085/1 "2015-01-06T01:34:02Z")

</div>

Strong evidence suggests that Mars had liquid water on its surface at one point in the distant past, but lost (a substantial % of it, along with its atmosphere) it because it didn’t quite have the gravity to hang onto it.

So…replace Mars 4.5 billion years ago with a twin of Earth. Does it still have liquid water now? An ice planet instead? [Assume no big moon like we have]