In a mission to gather data then clearly extra megapixels give you extra data. You cannot argue against that! We aren't talking amateur photography here where the quality of the shot is important and a decent lens beats higher megapixels, we are talking acquiring measurements of the amount of photons in a discrete spatial region. Clearly a higher resolution of sensor might allow scientists to see something not visible in lower resolution images. Although I do admit that in this case I understand the choice due to specification and testing, but to suggest that extra megapixels do not give more information is silly.
Actually, the opposite is true. Photon absorption/detection is a quantum event, and limited by probability. For a given sensor chip size (and technology generation), fewer, larger sensels are going to provide samples that are statistically closer to the Absolute Truth. (Averaging repeated samples will reduce the error further.)
Using a well-corrected lens of an appropriately longer focal length, and thus a narrower field of view, with or without panoramic stitching, will provide at least[1] the same linear resolution of a given subject, but with less sampling error.
[1] At least, since apochromatic correction is easier in longer focal length lenses provided that no super-wide-aperture bokeh heroics have gone into the design. Rectiliearity (the absence of barrel or pincushion distortion) is also easier to achieve. Flare can be reduced without inducing undue mechanical vignetting, increasing contrast.
