The other "buzz" at LPSC was about the seeming uncanny similarities between what Opportunity is seeing at Endeavour and what Curiosity/Mars Science Laboratory is finding at Glenelg/Yellowknife Bay, in Gale Crater. "It's fascinating that we're seeing such similar things at the two sites," said Squyres, who is a co-investigator on the new rover's ChemCam. "We're looking farther into the past than we ever have with Opportunity now. These are the oldest rocks we've ever looked at, and they're dramatically different from anything we've ever seen, but astonishingly similar to what we're seeing at the Gale Crater site. So we're looking into a very early period in Martian history, where the conditions were really rather different from what appears to have been the case through most of the planet's history."

John Grotzinger, of Caltech, principal investigator for Curiosity and an MER science team member, agreed and was equally enthusiastic. "If you just have the pictures telling the story, it looks like the same story. But then when you get the payload and Opportunity can do the RATing, we could see what's below the surface there," he told the MER Update.

"I'm really excited about this, because I think we're going to be able to now start what I hope will become an emerging field of comparative planetary habitability," Grotzinger continued. "This is what we did on Earth decades ago. You start looking at really old rocks. In the beginning, everyone thinks the rocks you see must've formed the same way. Then you get a little more data and you find out – gosh – there are different formation mechanisms here. Then you look at a few decades later and suddenly realize that there's a lot of diversity in early environments on Earth. And while some things look the same, but when you get into the details they start to look different.

"What's cool about this now is Opportunity is finding things – not just with the sulfates – but at Matijevic Hill where it's at right now," Grotzinger said. "If you didn't know the whole story about how Mars has had these different ages and how things occurred at certain times, then you might think maybe these rocks were right next to each other. But here they are – separated by a broad difference and may be separated by time. So I'm excited that we may learn that some processes that involve water may repeat themselves or occur in different places. That could [enable us] to begin to get the guidebook to thinking about how aqueous alteration works on Mars and where the favorable places are for habitability."

What's "really cool," Grotzinger said, are the "themes" that are appearing. "Whether it was the sulfates at Meridiani, the rocks that probably have clays at Endeavour or the rocks that we know have clays at Gale, they all produced concretions. There are some themes going on here and we're seeing a cast of characters emerge that are familiar. Maybe through those common elements we can recognize the difference between environments … and get us into the [areas] that look like the more habitable environments."