Page "Geography of Mars" Paragraph 27

The giant impact hypothesis, originally proposed in the early 1980s, was met with skepticism due to the impact area's non-radial ( elliptical ) shape, where a circular pattern would be stronger support for impact by larger object ( s ).

But a 2008 study provided additional research that supports a single giant impact.

Using geologic data, researchers found support for the single impact of a large object hitting Mars at approximately a 45-degree angle.

Additional evidence analyzing Martian rock chemistry for post-impact upwelling of mantle material would further support the giant impact theory.