Field encyclopedia
Marsipedia
What is known about Mars, cross-linked the way an encyclopedia should be.
Open the Mars articleThe picture is an original illustration, not a mission photograph.
- Articles
- 37
- Source pages
- 28
- Sheet date
- 26 Sep 2026
Featured article
Mars
The fourth planet from the Sun: a cold desert world with a thin carbon-dioxide atmosphere and two small moons.
Mars is the fourth planet from the Sun and the second-smallest of the eight planets. A mean radius of 3,389.5 km makes it a little over half as wide as Earth. The ground looks red because fine dust is rich in iron oxide.
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Field log
- 01A mean solar day on Mars, a sol, lasts 24 h 39 m 35 s.
- 02The sol clock uses the NASA GISS Mars24 equations, checked against their published example.
- 03Light time on a distance you type is that distance over 299,792.458 km/s. The long envelope is 22 minutes, not today's Mars.
- 04The Curiosity rover is 899 kg. Perseverance is 1,025 kg. Those are the rolled vehicles.
- 05On 20 March 2017 the Curiosity odometer stood at 16.0 km. A 2021 count found 4 broken grousers.
- 06Pressure at elevation is the datum pressure times exp(-z / 11 km). That is a screen, not a forecast.
- 07One kilogram of oxygen from carbon dioxide takes 2.75 kilograms of carbon dioxide. That is chemistry, not a plant.
- 08Six places share one dossier table. It can be sorted. It does not name a winner.
- 09Olympus Mons stands about 22 km above the datum. Relief from the northwestern plains can approach 26 km.
- 10NASA's September 2025 paper called a Jezero sample a potential biosignature, not a detection of life.
- 11As of this sheet, JAXA's MMX launch was still planned for 20 October 2026.