Today, I wanted to share a bit of the analysis we’re working on for Planet Four. Taking the Planet Four fan and blotch catalog from Season 1 and 2 of the HiRISE monitoring campaign, we’re now looking at what the average/dominant wind directions, derived for your classifications is telling us about the Martian south polar surface winds.
I wanted to show an example of what the science team is doing this. Tim Michaels has joined the science team and he’s an expert on climate modeling. We’re using the MRAMS (Mars Regional Atmospheric Modeling System) climate model/computer simulation to compare the fan directions to what direction is expected from the simulation. MRAMS is taking all the physics that we have about atmospheres and how we think these processes are working and computes what the atmosphere is doing and its conditions. We’re working on comparing the output of MRAMS to the wind directions we infer from the Planet Four fan directions.
Below is an example of one of the types of plots the team has been looking at. Here we show where the dominant fan direction is pointing in the full HiRISE frame from the Planet Four fan catalog. Think of this has telling you where the wind is headed. Each arrow represents a HiRISE observation image taken as part of the Spring/Summer monitoring season. The color of the arrows tell you which block of the Spring/Summer season the image was taken. For timekeeping on Mars, we use L_s, solar longitude, where Mars is located in in orbit around the Sun. L_s=180 is early Southern Spring. 220 is into early Southern Summer. We have 2 Mars Years as part of the current Planet Four catalog We plot the directions from each separately in the left and middle plot, and jointly all together in the right most plot. The left and middle plot show the topography that was used by the MRAMS model and the right most post shows the highest resolution topography measured by the Mars Global Surveyor’s Mars Orbiter Laser Altimeter.
Plots like this help the team look at the impact of topography and the structure of the local surface that might be contributing to how the wind blows. From this image we see that Giza is on the edge of an area where the elevation is dropping as we move more northward in latitude. Here we can see that the topography is likely playing a significant roll with the wind likely traveling from the highest elevations region (bottom of the plot) to the lower elevations. We’ll be able to compare with the detailed ouptut from the MRAMS simulation, but the topographic plots help us put the results from MRAMS in context. The simulation will tells us what direction it think the wind is blowing, but it won’t tell us necesarily why. These topographic plots help us add more explanation to the story.
Today we have a guest post by Tim Michaels. Tim is a research scientist at the SETI Institute who studies how the weather and climate of other worlds affects their surface features.
The Planet Four science team has recently been using the catalog of your fan markings to compare to the wind speed and direction estimated by computer calculations of how Mars’ atmosphere moves around. These wind estimates are calculated by a complex computer program known as a mesoscale atmospheric model, very similar to those that forecast the daily weather on Earth. There are no actual wind measurements in the southern polar regions of Mars, so we use these modeled wind estimates to better interpret what your fan markings tell us about the planet’s weather and climate.
The figure below shows an example of the modeled wind estimates near the Manhattan Classic fan site (86.4S, 99.0E) in the early evening at Ls 190. The area shown is about 135 km by 135 km, south is toward the upper right side, and every arrow is about 1.5 km apart (every model gridpoint; the numbers on the sides count these). This area is at the head (top) of the great south polar valley Chasma Australe, and the white topographic contours (in meters) show the upper reaches of that valley running downhill from center right toward the lower left. The arrows show wind direction and speed (arrow length, see the 10 m/s scale in the upper right corner). Wind speed is also indicated by the color of the arrows — cooler colors (like blue and purple) for the slower winds, warmer colors (like red and orange) for the faster winds. The fastest wind speeds in this scene are about 11 m/s.
You can see how the wind directions and speeds vary a lot across this area — those patterns change quite a bit with the time of day, as well. Our preliminary results show that the strong winds from the east near the center of this figure may be related to the formation of the fans in this area. Much more work still needs to be done to better understand what all of your markings of fans and blotches tell us about the winds on Mars, but we wanted to give you a glimpse of what the (invisible) winds that sculpt the fans may look like.