Scientists would be able to provide dates to the timeline of J | Astro Wonders

Scientists would be able to provide dates to the timeline of Jezero Crater that are far more accurate than those estimated from counting craters (the more craters there are, the older a surface is).

"The igneous rocks and the lake are both very old, in the vicinity of 3.7 billion years," Farley said. "I say that glibly, because that age is based on crater counting and the uncertainty on that is plus or minus half a billion years. That is an enormous uncertainty!"

Another key measurement that the samples could provide is how long Mars — or at least Jezero Crater — was wet for. The crater floor has a distinct lack of clays, which typically form when rock is exposed to a lot of water over a long period, meaning that either the water in Jezero was long-lived but shallow, or that the lake didn't exist for very long, at least not on geological timescales.

"I would hazard less than a million years," Farley said.

However, groundwater could have persisted for a much longer time, leaving its signature on the samples collected by Perseverance. Already the rover has detected salts, such as perchlorate, in the cracks between the rocks, which could have come from interactions with groundwater or even with frost melt, and therefore they could be much younger than the lake.

Now that Séítah and Máaz have been characterized as best they can be, Perseverance has departed for new pastures on the river delta that was the chief reason for landing in Jezero in the first place.

"We were expecting to land very close to the delta and begin our exploration there, but it didn't quite turn out that way," Farley said. So, after exploring the igneous rocks, Perseverance embarked on a record-breaking 3-mile (5 km) sojourn to reach the clay-rich delta, showing off the capabilities of its advanced autonomous navigation.

"We're now on the delta," confirmed Farley. "We've been working there for the past few months and we are clearly now on sedimentary rock that was deposited in the lake."

@thewonderofspace