Although the features haven't been proved to be biologically caused, they closely resemble features found in hot springs at El Tatio, Chile. So at the very least, we've got a probable ancient hot spring site, and one that potentially harbored life at some point. These features have been overlooked in Spirit's data for the last 10 years, give or take.
What else have we missed?
I don't know that I'd characterize it as "missing" something. When you consider the amount of effort that goes into the excruciatingly limited tools we have to send, the whole point of the endeavor is to make the raw data available to as many teams as possible. The fact that it's taking years for studies to come out indicates the depth of research, not the shallowness.
For many years I have dreamed of making a robot that returns from Mars with samples. I think it could be crowdfunded. Basically, get 100M in crowdfunding, then contract it."However, because of the challenges in obtaining unambiguous evidence in situ, coordinated microscopic and compositional analyses of samples returned to laboratories on Earth may be required to reach a robust conclusion as to the presence or absence of past Martian life in these rocks," Ruff and Farmer stated.
Maybe by 10. Spirit and opportunity cost $400M each. I guess it all depends on how selective your sample is, and whether or not the return rocket takes the needed fuel with it. I'm thinking of just grabbing whatever scoop you can get, and blasting off. Spirit weighs 400lbs. I wonder what is the lightest rocket that you can get to escape Mars with 1lb of soil.
The trick is getting back up the gravity well. I'm sure Kerbal Space Program could tell you. The fact that the Soviets started their discussion with an N1 does not fill me with confidence that it can be done economically. Something something 16 tons of hydrogen delivered to the surface of Mars. Something something fully-loaded Falcon 9 on the fucking surface.
About 20 years back I read an article in Analog proposing that terraforming Mars could most easily be effected by causing an artificial greenhouse effect via carpetbombing the place with millions upon millions of megatons of thermonuclear weapons. It'd sure free up some sequestered oxygen and nitrogen, you betcha.