It looked to be uniformly bland, which is why scientists chose it as the first rock to be examined up close last year by the Mars rover Curiosity: a run-of-the-mill volcanic rock, something to test and calibrate the rover’s instruments.

The rock turned out to be anything but ordinary, scientists reported last week. It is unlike any Mars rock previously examined and more like an Earth rock.

And as for the pile of windblown dust and soil that the rover spent weeks analyzing? It was not dry as dust, but contained water.

Such are the surprises that turn out to be a near constant of Mars exploration, according to six new papers on the red planet that appeared last week — five in the journal Science and one in The Journal of Geophysical Research: Planets.