Archive | April 2015

Crater Features

Since the launch of Planet Four: Craters a few weeks back, we have had several Talk posts regarding different features and markings that have been spotted in and around the craters themselves. This post will go through what some of these markings might be, and hopefully answer some of the questions you have had!

Recurring Slope Lineae (RSL)


Recurring slope lineae are narrow, dark markings found on steep slopes (like crater edges) that incrementally lengthen during warmer periods, then fade over cooler seasons and can recur over multiple Martian years. They can grow to be several hundred metres in length, and it has been suggested that they are caused by wet flow – originating from melted ice.

Active Gullies


Martian gullies are small networks of narrow channels, along with their associated down slope deposits, that occur on steep slopes, especially on crater walls. It has been suggested that they are formed by a flow of dry material, supported by a layer of dry ice just below the surface.

New Impacts

new impact

As the name suggests, these are craters that have been formed by impacts that have occurred in the near past. They are found all over the surface of Mars, and although they vary in size the smaller ones are much more frequent. They can be spotted by the darker coloured ejecta formed around them (due to the disturbed surface material that has yet to settle), or in some cases the presence of brighter patches – indicating where subterranean ice has been revealed.

If you have any other questions regarding some of the things you have spotted on Planet Four: Craters, please feel free to ask on Talk, and in the mean time please keep marking on!


Goodbye Inca City, Onward to Manhattan

Thanks to your help, the Inca City images we’ve been showing on the site for the past several months are complete, and we’re now back in the region known as Manhattan. We’ve been to Manhattan before, but that was during a different Martian year. HiRISE has been in orbit around Mars for almost 10 Earth years which equates to roughly 5 Martian years.  We’re showing new never-before-seen images on the Planet Four website right now. These observations are taken from HiRISE’s 4th Martian spring imaging the development of the windblown fans.

By examining the same region over and over again during different Spring seasons, we can study how this process of forming fans and geysers is evolving over time and how properties like topography, thermal inertia of the soil, presence of different types of spider channels, and changes in the Martian atmosphere impact the properties of the seasonal ice sheet and thus the formation and evolution of the seasonal fans (and by proxy the geysers that form them). In addition, the fan directions and lengths, as well as the presence of blotches, are an excellent probe of wind direction and strength throughout the Martian Spring. With your classification we will be able to see if the winds repeat the same each season or change direction.

For the rest of the South Pole we only have observations from Season 2 and Season 3 classified. With the completion of the previous set of Inca City images, we now have four seasons of fan formation mapping in Inca City. The extra two seasons doubles the temporal baseline we have on Inca City to look for changes and evolution in the fan formation process. The classifications you make now will help us have the same kind of dataset for Manhattan. Having fan and blotch maps for two regions with different topography and locations on the Martian South Pole will help us tease out which effects are due to local conditions and which ones are due to to the changes in the Martian climate (like more dust in the ice sheet).

Help classify the new images of Manhattan at

PS.  If you haven’t tried out Planet Four: Craters, do take a look and classify an image or two. Your classifications and feedback will help improve  the design of future Zooniverse projects.

Plane Four: Craters

Welcome to Planet Four: Craters!

Recently, a new version of the Planet Four project went live, and we are asking you to mark craters on the surface of Mars.

By counting the craters we will be able to figure out how old various geological surfaces are! This will be a big help for missions such as the 2016 NASA InSight experiment, which will use geophysical techniques such as seismology and heat flow to figure out how Mars has evolved. Knowing the age of the surface will help us to put a time-scale on that evolution.

Another aim of the project is to help improve the design of future Zooniverse sites.

When marking craters on Mars using this new version of Planet Four, you will be using one of three different classification interfaces. They each have different tools for you to use (on the left hand side of the page), and will ask you to complete tasks in differing orders for each image. Don’t worry! When you use one of these interfaces for the first time a tutorial will guide you through how to use it, in the same way the original Planet Four site did.

The reason for the different interfaces is that we want to know which one works the best, the one that you enjoy using the most and find the easiest to use, and gives the best crater marking results.

To find this out, we would really value your feedback. If you have a spare 15 minutes, there is a questionnaire on the Talk page (accessed through clicking the discuss button on the classify page) where you can answer questions and give your opinions about using the interfaces.

The information you give us will then be used to help design future versions of Planet Four, and other Zooniverse projects – so your opinions really count!

Get involved now at

Happy crater marking!