Archive | January 2014

Dry ice snowfall

About a week ago our colleague and a resident polar scientist on the Mars Climate Sounder (MCS) science team Dr. Paul Hayne wrote this Planetary society blog post. He talks about CO2 snowing on Mars! If you are interested to know why we think that it snows dry ice on Mars or what shape CO2 snowflakes are, go check it out! And let us know your thoughts on how it affects the areas that you are helping us to analyze!


The “Manhattan” region on Mars

We have now switched the data shown in Planet Four to focus on the Manhattan region, because it takes us quite a while to finish an area. (Everybody, keep clicking! Invite all your family and friends!)
Manhattan is a region within the ‘‘cryptic” terrain of the south pole of Mars. This terrain has been termed ‘‘cryptic” because even so its albedo (‘albedo’ measures the percentage of light reflected on a surface) darkens in the spring, indicating a better absorption of energy or even an absence of otherwise highly reflective ice, this terrain retains the 145 K temperature of CO2 ice until late in the season. This terrain is known to contain a host of phenomena that are inferred to arise from local gas jet activity.

The position of the Manhattan area within this cryptic terrain is indicated in the map below. Inca City by the way is such an interesting region because it shows all kinds of CO2 ice related activity while NOT being inside the cryptic region! Once we have finished Manhattan, we will switch to finish Inca City.

Cryptic region on the south pole of Mars. This is albedo (=reflectivity) data from the Mars Odyssey Thermal Emission Spectrometer (TES) draped over a MOLA (Mars Orbiter Laser Altimeter) shaded relief background showing considerable brightness variations. The low albedo region from 2 o’clock (300W) to 7 o’clock (160W), within the thermally defined extent of the seasonal cap (at lower right), is the cryptic region. Meridians and parallels are spaced every 30° and 5°, respectively. The zero meridian is pointing straight up. The indicated regions (with informal names) are areas that were selected for repeated coverage throughout the spring. Manhattan in particular was selected based on earlier observations from Odyssey’s THEMIS instrument

Cryptic region on the south pole of Mars. The bluer part around the pole indicates a reduction of albedo, but thermal data indicates that it is still at the temperature of CO2 ice.

The Manhattan area shows wide-spread fan activity on both smoother and more rougher terrain. An example is shown below.

Fans in the Manhattan region of the south pole of Mars

Fans in the Manhattan region of the south pole of Mars

When zooming in on an area without clear fan activity, as shown below in the zoom-in on area 2d, one discovers channels or troughs similar looking to the arms of the spider-shaped araneiform structures, but with one essential difference: They are not centralized, like the ones from araneiforms, where a set of arms meet in a more or less pronounced center. This pattern of troughs without center features has been dubbed ‘lace’ due to its visual apprearance.
Studying the fan activity in these areas with these underlying and neighboring roughness patterns will tell us if the fans develop differently in any way, either in resulting size distributions or over time. This hopefully will provide clues on differences in ground stability and therefore different gas transport ability during the CO2 activity, which can be compared with a araneiform-creation model.

A ''lace '' surface at the Manhattan region.

Zoomed in on area 2d from above. A ”lace ” surface at the Manhattan region.

All images of these post have been taken from C.J. Hansen et al. / Icarus 205 (2010) 283–295

One Earth Year of Planet Four in Images

Planet Four’s 1st birthday is on Wednesday. To celebrate and thank you for all of your help,  below are the 50 most popular images classified.  We tallied the number of people who favorited each image we’ve shown in the past year, and those in the gallery below in order came up on top. Click below on any of the images to get a larger view and to get a slide show to peruse through the entire collection. If you’re interested in any particular image, you can find all the images in this Talk collection. Help us celebrate by mapping some fans and blotches today at

Happy Aphelion

Today marks Mars’ passage through aphelion, its furthest point in its orbit from the Sun. At aphelion, Mars is moving slowest in its orbit while at perihelion, Mars is closest to the Sun and moving at its fastest velocity.  Mars has a more eccentric or elliptical orbit than Earth, and has the second highest eccentricity out of the 8 planets in our Solar System.


Plot of the inner solar system orbits (yellow dots are asteroid positions). You can see how eccentric Mars’ orbit is compared to the other inner Solar System planets – image Credit: JPL Solar System Dynamics/P. Chodas/ NASA/JPL

The Red Planet’s orbital eccentricity may actually be an important factor in  Mars’ climate. The Southern hemisphere right now is pointed away from the Sun and the carbon dioxide ice sheet is growing. Compared to the Northern hemisphere, Southern summers are  shorter (because Mars is at perihelion during that time) and the solar insolation is more intense while the Southern winters are colder and longer.  This dichotomy  may be responsible for why seasonal fans and blotches are abundant during the thawing of the carbon dioxide ice sheet in Southern Spring and Summer, but fans and blotches are spotted far and in between in the same seasons in the  Northern Hemisphere.

So far seasonal fans and blotches have mainly been spotted on the slopes of dunes at the Martian North Pole and tend to be smaller than their Southern hemisphere counterparts. One of the goals of Planet Four is to better study this. With your measurements of the frequencies, locations, and sizes of fans we’ll eventually compare Northern hemisphere fans to the occurrence and sizes of fans in the Southern hemisphere.