Which region of Mars is hypothetically suggested as the location for the ancient ocean, sometimes referred to as *Oceanus Borealis*?

Answer

Northern plains

Some models suggest water coalesced into a massive ocean in the vast Boreal region, known as the northern plains.

Which region of Mars is hypothetically suggested as the location for the ancient ocean, sometimes referred to as *Oceanus Borealis*?
MarsGeologyplanetsevidenceshorelines