Oceans on Mars?

Observations by the Viking orbiters and the MARS Global Surveyor seem to indicate that Mars may have had oceans in it’s past.

Nov 17, 2020

John Jennings, EASM Docent

Scientists have had multiple ideas about oceans on Mars. Observations by the Viking orbiters and the MARS Global Surveyor seem to indicate that Mars may have had oceans in it’s past as evidenced by an overall lower elevation and apparent shoreline in the northern part of the planet.   The Mars Orbiter Laser Altimeter (MOLA), which has accurately determined in 1999, the altitude of all parts of Mars, found that the hypothesized watershed for an ocean on Mars could cover three-quarters of the planet. In addition to the ocean, Mars seems to have many river valleys. Most of the following is based upon various analyses and modeling.

One possible approach to determining how much water has been lost on Mars lies in the ratio between deuterated water (D2O-heavy water) and normal water (H2O). Deuterium is a hydrogen atom with one extra neutron. Current analysis using this approach seem to indicate that Mars may have had enough water to cover up to 20 percent of the planet about 4.5 billion years ago.

               Figure 1 The Oceans on Mars       

The early ocean covering the northern hemisphere has been named the Arabia Ocean. Comparisons of the properties of the proposed sea floor with those of similarly sediment-laden surfaces on Earth support the idea of past oceans.

Potential shorelines formed before and during the formation of the Tharsis Bulge. These shorelines can be tracked for thousands of miles on Mars northern plains using spacecraft images. Some scientists’ modeling indicates shoreline deformations can be explained by the growth of Tharsis which occurred some 3.6 million years ago (Earth Years). The Arabia shoreline is believed to have been formed before or in the early stages of Tharsis Montes’s growth, whereas the later Deuteronilus’s shoreline arose during its late stages.

Figure 2. Tharsis Bulge Volcanos

The Tharsis Bulge consists of three exceptionally large volcanoes. Tharsis Montes volcanos probably released enough gasses to temporarily produce a

planet wide atmospheric pressure of about 22 psia (Earth is 14.7 psia). The Tharsis Bulge was so massive that it likely affected the planet’s moment of inertia, possibly causing a change in the orientation of the planet’s crust with respect to its rotational axis over time. Tharsis is believed to have formed at about 500N latitude and migrated toward the equator between 4.2 and 3.9 billion years ago. Such shifts, known as true polar wander (TPW), would have caused dramatic climate changes over vast areas of Mars. Olympus Mons is not part of the Tharsis Bulge but can be seen to the left of the Bulge.

Mars is believed to have lost its magnetic poles about 4 billion years ago but according to new research led by the University of British Columbia (UBC) has placed new constraints on when this magnetic field disappeared, indicating that the magnetic field existed sooner (and lasted hundreds of millions of years longer) than previously thought. Its loss resulted in the subsequent atmosphere and water, due to the Solar Wind.


  1. Nature, Volume 555 / Issue 7698, 29 March 2018 Oceans on Mars Formed Early
  2. NASA Research Suggests Mars….
  3. com (https://www.space.com/28742-ancient-mars-ocean-water-lost.html)
  4. University of Colorado at Boulder. "Ancient ocean may have covered third of Mars." ScienceDaily. ScienceDaily, 14 June 2010. <www.sciencedaily.com/releases/2010/06/100613181245.htm>.
  5. Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleysNature, 2010; DOI: 1038/ngeo891
  6. Universe Today  When Did Mars Lose its Global Magnetic Field?

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