An ancient Martian lake could have harbored a variety of microbial life around 3.5 billion years ago, a new study has suggested.

Scientists analyzed rocks from the Gale crater to reach their conclusion. Gale crater is a 96 mile wide depression that was once a vast lake. This site, according to scientists, is just perfect for studying Mars’s ancient climate.

“One of the things we’re really learning from Gale crater is that Mars—in its ancient geological history — really was home to environments that were very Earth-like in their quality,” study author Joel Hurowitz told Newsweek.

“We’re talking about a lake that was being fed by freshwater rivers, it was a standing body of water that was there for a long period of time that had lake chemistry very similar to what we see on Earth.”

“This idea that Mars in its early history might have been a more Earth-like place—we’re demonstrating one the ground that this really was the case. We can place ourselves onto the surface of another planet and imagine what it would be like at one time in its history—and it would’ve looked quite similar to what Earth looks like.”

In this study, researchers analyzed rocks gathered by Curiosity from various depths. Curiosity landed inside the 93-mile-wide Gale Crater in 2012 and since then, it has been drilling and analyzing rock samples. The rover has discovered the chemical ingredients — like carbon, nitrogen, oxygen, phosphorus, and sulfur — on Mars.

To reconstruct the red planet’s past climate, Hurowitz and his team measured how much aluminum each layer contained, versus minerals like sodium and calcium which easily leach out of the rock. They found that the upper layers of the Martian lake were awash in oxidizing agents, while deeper layers contained reducing agents. The lake also provided a variety of ecological niches that microbes on Earth would have thrived in.

“This lake presented a menu of options for microbial life, if it was present,” says Hurowitz.

“We’re learning a lot from Curiosity about how to go to that next level.”

“I don’t think we expected that we would be able to understand this much detail about the chemical conditions in the lake that existed 3.5 billion years ago. This was actually a very Earth-like environment.”

The findings suggested that Mars had the physical, chemical, and energetic ingredients to support life between 3.8 and 3.1 billion years ago.

The detailed findings of the study have been published in the journal Science.

[Original Research published in Journal Science.]