# @nasa on Instagram

- **Type:** Image
- **Original URL:** https://www.instagram.com/p/CcNfhnZLcFt
- **Gondola URL:** https://gondola.cc/posts/11732938-nasa-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/thumbnails/c76e46e775.jpg
- **Posted:** 2022-04-11T12:30:11.000+00:00
- **Account Owner:** NASA (@NASA) — https://gondola.cc/NASA

## Caption

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

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## Tags

nasa, space, mars, mro, maps, jpl, longitude, redplanet, crater

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