The next stop on our history of Mars mapping is the German astronomers Beer and Mädler. Working in the 1830s and 40s, they took Mars maps a significant step further, establishing a coordinate system and a prime meridian which is essentially what we use today. Here is the map made from observations in 1830 (published 1831) when the southern hemisphere was visible (as for Herschel). The south pole in in the middle, 30 north at the outer edge. #maps#Mars#Beer#Mädler