Four years ago, an underwater volcano erupted in the South Pacific, creating a new island. And NASA took notice.

The island’s evolution could hold clues to how water might have shaped similar features on Mars billions of years ago, NASA officials believed, so the space agency began collecting satellite photos to track how the elements were carving and clawing away at the land.

The images yielded insights into how the island was eroding, but the story they told was limited. NASA could wring more information from those photographs with measurements taken from the ground, but James Garvin, the chief scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., could not justify the cost of sending a team. Then an opportunity presented itself.