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.