A study of the Deuteronilus and Arabia contacts on Mars reveals that the contacts may have started out at equipotential levels but have been deformed by a post-contact true polar wander (TPW) event. For this to be possible an initial TPW event, driven by Tharsis, must have occurred. There are two scenarios for the Tharsis driven TPW. In the first it formed at the pole and rotated the planet so it would be equatorial causing a large TPW wander event; in this case a small load is needed to cause post-Tharsis TPW. In the second, it forms near its current location driving a small TPW; in this case a massive load is needed to cause any post-Tharsis TPW. The most compelling solution found is an initially large Tharsis-driven TPW…show more content… These shorelines were used to hypothesize a Paleo-Ocean which would explain the terrain in the northern hemisphere (Brandenburg). Clearer data came with the Mars Global surveyor in the 1990’s; however, since the hypothesized shorelines did not follow equipotential surfaces the data was inconclusive whether or not there had been oceans on Mars. Then the Mars Orbiter Laser Altimeter studied erosion of the lowlands and found that it was consistent with mass sublimation and that the hypothesized ocean would have covered much of the planet’s surface. In 2007 true polar wander was used to explain the shoreline deformation seen in 1998. In 2009 studies on the valley networks of Mars revealed a rainfall-level pattern which had a maximum along the shoreline and which steadily decreased moving inland – which is again, consistent with a large ocean. In 2010 a study showed that the majority of deltas on the planet are found along the proposed shoreline. In 2012 MARSIS collected data which showed that the dielectric constant of the lowlands is consistent with that of low-density sedimentary and ground ice deposits, not igneous rocks determining that the resurfacing process of the lowlands was not predominantly magmatic (Mouginot).
The deformation of long-wavelength shorelines due to TPW
The Tharsis bulge is the largest volcanic system in the Solar