The Martian crater marks the spot ❌ You’re looking at 0° longitude on Mars—the Greenwich Observatory equivalent on the Red Planet. The Greenwich Observatory marks Earth’s Prime Meridian, which is is a north-south line that defines where east meets west, and is used as the zero-reference line for astronomical observations. The larger crater that sits within this crater, called the Airy Crater, originally defined zero longitude for Mars, but as higher resolution photos became available, a smaller feature was needed. This crater, called Airy-0 (zero) was selected because it did not need to adjust existing maps. This image was captured by the High-Resolution Imaging Science Experiment (HiRISE), on the Mars Reconnaissance Orbiter. The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. Credit: NASA/JPL-Caltech/University of Arizona #NASA #JPL #Mars #RedPlanet #Longitude #Space #Crater #MRO #maps