Why it is red
The surface of Mars is covered in dust rich in iron oxide — essentially rust. This fine dust is blown across the planet by winds, creating the characteristic color visible from Earth with the naked eye.
Evidence of water
Orbiters and rovers have recorded:
- Ancient valley networks and deltas, most clearly at Jezero crater where Perseverance is currently operating
- Minerals that only form in the presence of water, such as clays and sulfates
- Exposed water ice at the poles and subsurface ice at mid-latitudes
The current picture: about 3.5–4 billion years ago, Mars was much warmer and wetter.
Where the water went
Mars is small, so its core cooled quickly and its global magnetic field shut down early. Without this shield, solar wind eroded the atmosphere over billions of years. The MAVEN mission has measured this atmospheric loss, which continues to this day.
The drop in pressure means liquid water is no longer stable on the surface: some escaped into space, while some froze underground.
Extreme terrain
- Olympus Mons — a 22 km high volcano, nearly three times the height of Mount Everest
- Valles Marineris — a canyon system 4,000 km long and up to 7 km deep
- Two small moons, Phobos and Deimos, likely captured asteroids
Read more
References
- [1]Planetary Fact Sheet — NASA NSSDC (2024)
Image: ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA, CC BY-SA 3.0 IGO — Wikimedia Commons, CC BY-SA 3.0 igo.
