The Navua, Ausonia and Hadriacus Paleolake systems in NE Hellas.
Paper in Astrobiology by Hargitai, H.I.; Gulick, V.C.; Glines, N.H.
This figure shows a lake on Earth (in the Andes region, left) and on Mars (within an impact crater, right), where the depression and lake filling deposit morphologies are similar but formation mechanisms were likely different (winds played a role on Earth and fluvial processes on Mars). However, we believe that the layered deposits that filled this crater on Mars are sediments that were transported by a paleoriver and laid down in lacustrine conditions (ponding water) that existed within this crater when the channel was active.
The blue feature is a small paleolake basin that connects an inlet and and outlet channel. The channel system North of this lake (“c”) is not a channel but a ridge: it might have been topographically inverted but it is more likely that these channels are inflated lava flows. The letters “d” show erosional (likely fluvial) channels. Fluvial channels, lakes and lava channels sometime occur next to each other. On Earth one such place is in Saudi Arabia.
In and out: This is a degraded impact crater with two delta-like deposits (white outlines) and three connected channels (blue lines). The channels on the right transported water and sediments into the crater and the channel on the lower left carried water out of the crater. The outlet channel is higher than the crater floor so it had to be filled at least 42 m high so that water reached the outlet channel’s entrance level at the crater’s degraded rim.
We observe only the final stages of paleolakes on Mars, hundreds of million orperhaps billions of years after these of lakes had been dried out. On Earth we can follow lake transformation in satellite images (in this figure in the high Andes). Martian lakes likely had similar life cycle(s): they were filled and dried from time to time, depending on local climatic conditions. Observe how the water level is related (or not) to snow on the top of a nearby volcano.
This is the timeline of potential lake activity in the NE Hellas region on Mars. Potential paleolake depressions formed and resurfaced over the last almost 4 billion years repeatedly, under different climatic conditions. Lakes and connected channels were fed from different sources: some directly from precipitation (snow), others from the water transported by channels or from ground water. (Mars-Earth Timelines by Ginny Gulick, SETI Institute)
This map shows the Navua Valles region Northeast of Hellas Basin (the Basin’s floor is on the lower left, shown in bluish colors). Blue lines represent channels and valleys that once transported water down slope. White outlines show fluvial deposits where flowing water laid down sediments. Light blue areas show potential paleolakes: depressions that were potentially filled by water.
A=Navua A drainage system,
B= Navua B drainage system.
Navua A system was fed by precipitation, likely snow. Both drainage systems emptied into the Hellas Basin floor.
Read about the Navua Valles drainage system in our previous paper.
This figure shows that most lakes were active (almost?) simultaneously 3.6 and 1 billion years ago.
Perspective view of an unnamed crater that is crossed by Navua A channels. The crater was already degraded when channels cut into its rim and formed a lake in its deepest parts, in ancient times. In recent times a dense network of regular mounds developed within this crater, probably related to a novel appearance of subsurface ice, not related to the channels. (Perspective view by Natalie Glines)
Citation: Hargitai, H.I. Gulick, V.C., Glines, N.H. 2018 Paleolakes of Northeast Hellas: Precipitation, Groundwater-fed, and Fluvial Lakes in the Navua–Hadriacus–Ausonia Region. Astrobiology 18(12)
Here is my metro map of the Navua drainage systems. I really like maps.