Daichi Fujii, who is an astronomer and curator of the Hiratsuka City Museum, has some motion detecting cameras set up, near Mount Fujii, to catch the goings-on the moon.

During a clear night on the 16th of September 2022, Fujii’s camera’s caught a green light cruising across the night sky. “It’s the Martians coming back to get my moon pies!” is what Fujiii most likely said after looking at the footage.

It wasn’t those pesky Martians, though, coming back to raid Fujii’s pantry again of the moon pies. It was NASA. NASA’s satellite, Ice, Cloud and land Elevation Satellite 2 (ICESat-2) has a lidar that shoots off, at a rate of 10,000 times per second, six green beams of light from space.

According to the folks over at the National Oceanic and Atmospheric Administration (NOAA), a lidar (Light Detection and Ranging) is an instrument that has a laser, scanner, and GPS that are used to locate and/or measure the Earth’s land and water.

Lidars come in two types. One type is the topographic and the other is the bathymetric. The topographic uses the infrared colors to measure the land. The bathymetric uses the green lasers to measure the water. Therefore, when Daichi Fujii saw the green lasers cruising by in the night sky, he saw the bathymetric lidar shooting down to measure the Earth’s waters.

The specific body of waters the lidar was measuring were the polar oceans. The polar oceans are the Arctic Ocean and the Southern Ocean. The folks over at NASA say that ever since September 2018, they’ve been using the lidar attached to the ICESat-2 to measure the waters in the polar oceans, amounts of ice in Greenland and Antarctica, the freshwater we have, and the amount of land that is still around here.

In the 4+ years that NASA has been doing its research, no one has ever seen the lil’ green lights cruising across the sky because the conditions in the night sky haven’t been right. “To see the laser, you have to be in the exact right place, at the right time, and you have to have the right conditions,” is what NASA quoted ICESat-2 instrument scientists Tony Martino as saying.

And for Daichi Fujii, everything was exactly right…especially since those pesky Martians didn’t get his moon pies!