NASA's Curiosity Mars rover discovers evidence of ripples from an ancient Red Planet lake (images)
www.space.com
The ripples suggest that the lake was free of ice at one point.

From the Article:

“The Curiosity rover discovered evidence for long-lived ancient lakes in 2014, and now 10 years later Curiosity has discovered ancient lakes that were free of ice, offering an important insight into the planet’s early climate.”