Cloudspotting on Mars: Shapes

How does the Imaging Ultraviolet Spectrograph (IUVS) see clouds?

Unlike cameras that look at visible wavelengths of light to take pictures of Mars, the Imaging Ultraviolet Spectrograph (IUVS) measures ultraviolet light. From its position in orbit above Mars, it creates images looking down on the illuminated disk of the planet, "seeing" the relative reflection and absorption of the Sun's UV rays by the Martian atmosphere and surface. Because clouds are strong reflectors of ultraviolet light, they stand out as white shapes against the darker planetary surface of rocks and dust.

Of course, the IUVS instrument doesn't just look for clouds -- it actually has 5 separate observing modes, which measure vertical profiles of atmospheric chemical species (such as CO2, CO, and O3), as well as characterizing the upper atmosphere of Mars as it escapes (somewhat like evaporation from the top of a boiling pot). These observations help us understand the weather and climate, including dust storms -- a defining feature of Mars's atmosphere.

When did IUVS begin measuring the atmosphere?
In 2014 -- it's been orbiting Mars for almost 10 years! This long period of observations is what allows us to investigate how Martian clouds change with the season and from year-to-year.

What is a Mars Year (MY)?
A Mars year takes 687 Earth days. Mars Year 0 (MY0) is defined to start on May 24, 1953. Instead of named months of the year we use on Earth, we track solar longitude, "Ls" (pronounced "ell sub ess"), which corresponds to Mars's position in its orbit around the Sun. Here is a tool to convert MY and Ls to an Earth date, and from Earth date to Mars MY and Ls. Check out this article to learn more.

You can find the MY and Ls of each image you classify by clicking the "i" metadata button below the image on the bottom right.

Why isn't Mars round in the project's images?
Our instrument constructs images by scanning across the disk of Mars, rather than snapping a single photo. This scanning motion is read out, and then the instrument moves to scan a new area. The result of this is that the disk of Mars appears as though it is sliced up, with some sections of the image repeated over the course of the process (typically near the edges next to the adjacent scan).

Where can I find the raw data?
The data used to create the images you see in this project -- IUVS apoapse level 1b files -- are available at the Planetary Data System. Processing these data from their native state to the images you see is a nontrivial task, and while some code is available on Github (link coming soon), feel free to contact us for guidance on using these tools yourself. We're always interested in collaboration, building new tools and better utilizing the data we have in hand, so if you would like to help please do not hesitate to contact Matteo Crismani (matteo.crismani@csusb.edu).

How do clouds form on Mars?
Clouds form from frozen water and carbon dioxide (CO2) on Mars. While we think of Mars as a cold and dry planet, the atmosphere does contain some water vapor. If a parcel of Martian air with water vapor becomes cold enough, water vapor can condense into an ice crystal. The cold temperatures and low pressures in the atmosphere lead water vapor to transition straight to ice instead of liquid droplets. It is uncommon for clouds to form from the main constituent of the atmosphere of a planet. But in some locations on Mars, especially at high altitudes, temperatures can drop low enough such that carbon-dioxide (the main constituent of Mars' atmosphere) can form ice crystals. One more ingredient is important for cloud formation: cloud condensation nuclei, or particles on which water or CO2 can condense. These can be dust particles or, for CO2 clouds, water-ice particles, or maybe even "meteoric smoke particles" that come from meteors that enter the atmosphere from space. Differences in the compositions and particles of the clouds lead to differences in how these clouds warm or cool the atmosphere.

Do the cloud types seen here form on Earth?
They do! In addition to all of the cloud types listed in this project, which are analogous to those seen on Earth, there are many more types that can exist only at Earth. Some of this is because Mars lacks liquid water clouds and some haven't been seen yet because we lack the necessary spatial resolution. Perhaps you will identify a new cloud type at Mars! Learn more in this helpful explainer for Earth clouds.

I can't quite tell, is what I see is an cloud?
We suggest only labeling a cloud if you are confident that the white object in your image is not ice on the surface. Use the geography map (the fourth view) to verify that you are not looking at one of the Northern or Southern poles. Check out the Field Guide for many examples that might help. We also recommend discussing images you have questions about with others in the Talk board.

I made a mistake, how can I fix it? How can I redo an image?
Don't sweat it! Many people will look for clouds in each image, so it's ok if you think you made a mistake in a previous image. Unfortunately, there is no "redo" button, so once you click "Done", your markers are set. Put it behind you and move on! But maybe take an extra minute to click back through each frame and double check your markers on the next one.

Getting involved
How do I join the Cloudspotting on Mars Community?

If you'd like to get involved at a deeper level, we invite you to join our community. Just reach out to us at cloudspottingonmars@gmail.com and ask to join the community. Looking forward to hearing from you!

You can also check out our Github page and our blog for more information and opportunities to do more.