Is it true that Mars used to look like Earth?

Ancient Mars resembled Earth in some important landscape features: it had flowing water, lakes and river deltas. However, saying it simply looked like Earth overstates what scientists can reconstruct about the planet as a whole.

NASA describes ancient river valleys, deltas, lakebeds and minerals formed in liquid water. Independently, ESA's Mars Express observations identify landscapes carved by flowing water and glaciers. Curiosity's findings also indicate repeated lake environments at Gale Crater more than three billion years ago.

These findings establish a wetter past, not an exact Earth-like appearance or a continuously warm global climate. NASA research also points to possible ice-covered lakes and alternating environmental conditions. Images of a blue, Earth-like ancient Mars are reconstructions whose details depend on assumptions, rather than direct records of its appearance.