Don’t identify water ice from a Mars orbiter image’s color alone. First identify the instrument and data product, then inspect calibrated spectral or thermal measurements and account for atmospheric haze and surface dust. CRISM reflectance spectra and THEMIS visible and infrared images measure different properties, and a frost signature does not by itself establish that the frost is water ice.
Start by identifying what the image measures
CRISM and THEMIS data are not interchangeable. CRISM’s targeted MTRDR products include map-projected reflectance cubes, wavelength information, summary and browse products, and processing details. Use the reflectance cube and its wavelength data for a spectral interpretation; a browse image is a viewing aid, not a substitute for the measurements. NASA’s Planetary Data System describes these products and their processing at the CRISM MTRDR archive.
THEMIS has two distinct imaging systems: a five-band visible subsystem and a 10-band thermal-infrared subsystem. The Arizona State University Mars Space Flight Facility lists visible bands centered at 0.425, 0.540, 0.654, 0.749 and 0.860 μm, and infrared bands centered at 6.78 μm (two filters), 7.93, 8.56, 9.35, 10.21, 11.04, 11.79, 12.57 and 14.88 μm. THEMIS image resolution is 19 m/pixel for visible data and 100 m/pixel for infrared data; those are different spatial scales as well as different wavelength ranges. See the THEMIS mission FAQ.
A visible false-color image, a thermal-infrared image and a CRISM reflectance cube therefore cannot be read with one shared color key. Before interpreting a feature, note which instrument and product produced it, what bands or wavelengths are displayed, and whether the data are calibrated.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitches#1 Best Overall
- Mars in Motion – A Realistic Look at the Red Planet - Golden-red surface tones with volcanic ridges and weathered terrain bring Mars to life. An inspiring piece for space lovers and science fans alike.
- Self-Rotating Technology Powered by Light - MOVA’s patented design silently spins the globe using ambient light and the Earth’s magnetic field — no batteries or cords required.
- Premium Build with Seamless Movement - A fluid-suspended inner globe rotates within a clear acrylic outer shell, offering a smooth, almost magical visual experience.
- Perfectly Sized for Personal Spaces - Measuring 4.5 inches in diameter (about softball size), it fits beautifully on desks, shelves, and side tables as a compact cosmic accent.
- Gift-Worthy for Dreamers and Thinkers - A thoughtful present for science enthusiasts, educators, students, and anyone fascinated by space. MOVA Globes spark imagination and lasting conversations.
Why color alone cannot identify ice or dust
False color is a way of displaying selected measurements, not a universal label for a material. NASA’s THEMIS example “DCS Color near Mare Cimmerium” uses a decorrelation stretch to emphasize differences among three bands. In that particular scene, green and blue areas indicate dust, while faint blue areas may be thin water-ice clouds. The image was a preliminary release without radiometric or geometric calibration, so its colors should not be transferred to other images as a general ice-versus-dust rule.
A second NASA example, “Ice Surfaces In False Color,” describes ice or frost as bright blue and dust-mantled ice as red or orange in that north-polar THEMIS false-color product. That image, too, was a preliminary uncalibrated release. Its color differences may reflect fresher, less dust-covered upper ice. These examples show how a specific processing recipe can make a pattern visible; they do not establish a universal palette.
Rank #2
- Mars in Motion – A Realistic Look at the Red Planet - Golden-red surface tones with volcanic ridges and weathered terrain bring Mars to life. An inspiring piece for space lovers and science fans alike.
- Self-Rotating Technology Powered by Light - MOVA’s patented design silently spins the globe using ambient light and the Earth’s magnetic field — no batteries or cords required.
- Premium Build with Seamless Movement - A fluid-suspended inner globe rotates within a clear acrylic outer shell, offering a smooth, almost magical visual experience.
- More to Explore - Our larger Mars globe offers richer surface detail and stronger visual presence, ideal for offices and display cabinets.
- Gift-Worthy for Dreamers and Thinkers - A thoughtful present for science enthusiasts, educators, students, and anyone fascinated by space. MOVA Globes spark imagination and lasting conversations.
Use CRISM spectra, while checking for atmospheric haze
For CRISM, examine reflectance across the available wavelengths rather than deciding from one weak absorption feature or a rendered browse product. MTRDR processing corrects for photometric, atmospheric and instrumental effects and provides wavelength and processing information, but it does not remove all scattering by dust and ice aerosols.
Atmospheric water-ice haze can produce weak absorptions near 1.5 and 2.0 μm. A feature at those wavelengths is therefore not, on its own, proof of exposed surface water ice. Compare the broader spectral behavior and consider the scene’s atmospheric conditions and observation geometry. The PDS description also notes that aerosol effects can be strongest at shorter wavelengths and can affect iron-mineral absorptions.
Rank #3
- Globe Diameter : 24cm / 9.5"
- Item Size : 9.5"D X 14"H X 10"W / D 24cm X H 36cm X W 26cm / Diameter X Height X Width
- Name : Explorer Red Mars Globe, 24cm/9.5"
- Color : Red (Mars surface) / Uses images from NASA
- Base Material : Plastic Dark Brown (ABS)
The CRISM archive excludes certain high-opacity scenes, including scenes above the archive’s example thresholds of dust opacity τ > 1.39 and ice opacity τ > 0.28. Those are archive-specific processing thresholds, not universal cutoffs for classifying an observation as dust or ice. Aerosol loads can still differ among overlapping scenes, so spectra from different observations may not be directly comparable without checking their conditions.
Use THEMIS infrared and visible context together
THEMIS thermal infrared data can provide evidence that visible imagery misses. The mission FAQ explains that water and ice absorb in the infrared bands THEMIS uses. But infrared data also have important blind spots: a surface dust layer as thin as about 100 μm (0.1 mm) can obscure thermal-infrared signatures from material beneath it. At 14.88 μm, the Martian atmosphere is opaque, so THEMIS cannot see the surface in that band.
Rank #4
- Size : 12"D X 18"H X 13"W / D 30cm X H 45cm X 33cm
- Material(Globe / Meridian / Base) : Plastic Dark Brown (ABS)
- Technique : Vacuum formed (Erasable markers ; Write-on, wipe-off)
- Language : Latin & English, Color : Red, Scale : 1 / 22,640,000, Rotation axis : 23.5°
- Over 600 place names including. Includes illustrations.(Landers/Rovers)
A missing infrared signature does not rule out buried or dust-covered ice, just as an infrared frost-like signal does not identify the frost’s composition. Pair infrared observations with visible imagery and, where available, spectral data. The modalities can constrain different parts of the interpretation, but none should be treated as a standalone answer in every scene.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Distinguish surface frost from atmospheric ice and identify its composition
Not every ice-related observation concerns water ice on the ground. CRISM limb spectra, for example, cover 0.4–4.0 μm and are used to characterize mesospheric aerosol composition and particle properties, a different task from mapping surface ice in a reflectance cube. NASA’s 2019 NTRS summary of CRISM limb observations describes that atmospheric use.
Recommended Free Tools
Surface frost can also be mixed with dust or consist of a different kind of ice. In a May 5, 2022 report, NASA JPL described a dawn frost case that was largely carbon-dioxide frost; researchers proposed that fine dust mixed into the frost helped obscure it in visible imagery, while infrared observations revealed it. This is a caution against labeling every frost-like signal as water ice. See NASA JPL’s report on the observation.
A practical workflow for interpreting a candidate feature
- Identify the instrument and product. For CRISM, establish whether you have a targeted reflectance cube such as an MTRDR or a browse or summary product. For THEMIS, determine whether the image is visible or thermal infrared.
- Check processing and calibration. Read the product’s wavelength, processing and calibration information. Treat preliminary, uncalibrated false-color examples as visualizations, not as calibrated measurements.
- Inspect measurements across bands or wavelengths. For CRISM, assess the full reflectance spectrum. Do not classify surface ice from a single weak feature near 1.5 or 2.0 μm without considering atmospheric water-ice haze.
- Assess dust and atmospheric conditions. Check for aerosol effects and differences between overlapping observations. Archive screening does not mean that all remaining scenes are free of dust or ice aerosol scattering.
- Compare available modalities. Use THEMIS visible context alongside infrared data when available, while allowing for surface dust that may screen thermal signatures. Add spectral evidence where the observation permits it.
- State only what the evidence supports. Name the instrument, product, relevant bands or wavelengths, calibration status, and whether the interpretation concerns atmospheric aerosol, surface frost or buried material. If the evidence establishes frost or ice but not its composition, do not call it water ice.
What an image can—and cannot—settle
There is no source-supported accuracy score showing that CRISM or THEMIS is universally better at classifying a scene as water ice or dust. The answer for an individual feature depends on the actual observation, product version, wavelengths or bands, geometry and atmospheric context. A color pattern or one weak spectral feature can suggest an interpretation; a defensible claim requires the measurements and caveats that support it.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
