This artistic image shows Spirit’s approximate position and location in Troy, on the west side of Home Plate. Artist Astro0 has placed a two-dimensional MER into a scene created by pictures taken by the real rover. Although the angles are admittedly a little off and the disturbed soil isn't quite right, it offers the casual reader a glimpse into the present scene on Mars.
About three months later, in June 2010, ostensibly while Spirit was in hibernation, Richard Morris and MER Science Team colleagues announced that Comanche is harboring magnesium iron carbonate, and a lot of it. In their Science journal article, they theorized that it could have been produced by a hydrothermal system.
It was evidence for a past watery environment more suitable for life than any other either MER had found, a place where near neutral water existed, water the likes of which we would drink on Earth. And it was a discovery Squyres called “one of the top five findings of the entire mission.”
That carbonate discovery led to more questions for Ruff. “One of the interesting problems with the Comanche hypothesis is that is requires carbonates to have been present somewhere else and some other time in Gusev Crater from which you could then pump hydrothermal fluids through and dissolve the carbonates and re-precipitate the carbonate in Comanche,” he noted. “Well, where were the original carbonates?”
Ruff and a few colleagues did further research and published a paper in 2014 hypothesizing that the carbonates could have come from an evaporating, ephemeral lake or lakes recurring in Gusev. “The carbonate really is potentially consistent with an evaporative environment, maybe recurring multiple times that could have left carbonate behind in the rocks of Comanche,” he said. “It’s a reasonable hypothesis that responds to a set of observations made by both Spirit and from orbital instruments.”
Ruff has been rigorously challenged throughout the years. But he is driven. “I sometimes feel like a voice in the wilderness, but I will continue to pursue the science from Spirit, because it’s important and I want others to understand the richness of the dataset and what else we else we may be able to find,” he said. “Even though we quit acquiring observations in late 2010, for me this dataset is a gift that keeps on giving even well after the passing of Spirit,” Ruff continued. “Even now 14 years down the road, I can go back to Spirit’s observations and see new things and understand other things better.”
For a little more than a year, engineers tried repeatedly to get Spirit to respond to signals. They sent more than 1300 commands to the rover through the DSN’s X-band, and the ultra-high frequency (UHF) relay communications systems with Mars Odyssey and Mars Reconnaissance Orbiter, each an attempt to elicit a response from the rover. Each was met with radio silence.
On Monday, May 23, 2011, NASA and JPL officials announced the end of the official recovery effort. The last of the sequences prepared for a final intensified effort, were scheduled to be sent early May 25, 2011 PDT. "We always knew we would get to this point," noted MER Project Manager John Callas in May 2011. "We're here today because we wore Spirit out."
In six+ years of roving, Spirit drove 4.8 miles (7.73 kilometers), more than 12 times the goal set for the mission, chalked up a number of “firsts” along the way, and demonstrated a mechanical kind of MER mettle that set the bar high for future Mars rovers. "What's most remarkable to me about Spirit's mission is just how extensive her accomplishments became," said Squyres.
The MER team mourned Spirit and also properly celebrated all the rover had accomplished in a press-invite gathering at Caltech, and later with a more private Irish wake that was, as Fraeman reviewed it, “pretty awesome.”
