The largest of these on Mars is Hellas Planitia, more than 1,3000 miles wide and 3.78 miles deep
... now, Hellas' great depth makes it one of the warmest places on Mars ... 
pressure has been measured at more than 10 millibars, more than twice... [DOC] [TLE] Atlas of the Universe - Scribd [PAR] He also measured the positions of the planets, particularly Mars.