Use NASA’s free browser tools to find named lunar craters, inspect their shape and measure their size. To determine whether a crater is genuinely new, compare orbital images taken at different times: a crater that is unfamiliar in one view is not necessarily a recent impact.
Choose the right NASA tool
| Tool | Best for | What it offers |
|---|---|---|
| Moon Trek | Guided exploration and surface measurements | NASA describes 3D flyovers, spacecraft data, feature search, data layers, downloads and metadata, along with tools such as distance measurement and elevation plots. Its About page reported version 3.6.29 when accessed; the interface and version may change. |
| LROC QuickMap | Custom map exploration of Lunar Reconnaissance Orbiter (LRO) imagery and map products | NASA describes it as a web mapping and analysis interface for LRO lunar maps. Available LRO products include global, polar, regional, shapefile and topographic products; the exact layers and metadata depend on the selected product. |
| MoonDiff | Checking for possible changes between image dates | The project invites citizen scientists to compare older and newer orbital images to look for new craters and missing spacecraft hardware. It also shows examples of apparent changes that are misleading. |
NASA’s Moon Interactives page is a starting point for Moon Trek and QuickMap. For named-crater practice, NASA also provides the downloadable Investigating Impacts activity. A printed lunar atlas can be a useful optional label reference, but it is not needed to explore imagery on screen.
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Find a named crater and measure it in Moon Trek
NASA’s classroom activity demonstrates a repeatable workflow. Interface locations can change, so treat the activity as a guide to the functions rather than a guarantee that controls remain in the same place.
- Open Moon Trek. Start from NASA’s Moon Interactives page and launch Moon Trek.
- Choose a view. Navigate with the globe or map projection, then pan and zoom to the area you want to inspect. The NASA activity names 3D Globe, North Pole Map, Global Map and South Pole Map options.
- Show names. Enable the Nomenclature feature so named lunar features appear on the map. Search for a crater name, or use the activity’s example, Dawes. It also suggests practicing with Moltke, Tycho, Copernicus, Clavius and Theophilus.
- Measure rim to rim. Use the line tool to draw across the crater’s widest span, from one rim to the other. Record the displayed measurement and the data layer you used.
- Trace the rim. Use the polyline tool to follow the crater edge if you want to estimate its circumference.
- Inspect a cross-section. Draw a profile line from beyond one rim, across the crater, and past the opposite rim. The resulting elevation profile helps show the relationship between rim, wall and floor.
These are measurements of the displayed data and your chosen line placement. They are useful for exploration, but should not be presented as new scientific measurements without checking the underlying data and method. Moon Trek’s About page describes its data-layer, search, download, metadata, distance and elevation functions; consult the product metadata when interpreting a particular result: About Moon Trek.
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Read crater shape, scale and lighting together
NASA defines lunar impact craters as “the depressions left behind after an asteroid, meteoroid, or comet collides with the Moon” in its Moon Craters guide. Shape and scale help describe what you see, but a diameter alone does not establish a crater’s age or explain every detail of its formation.
- Simple craters are generally smooth, bowl-shaped features with round floors. NASA describes them as typically no more than around 6–9 miles (10–15 km) in diameter.
- Complex craters are generally around 9 miles (15 km) or more across and may have central peaks, terraces and flatter floors. The size descriptions overlap near the boundary, so do not classify a crater from diameter alone.
- Impact basins are much larger structures, more than 186 miles (300 km) across. NASA reports that the Moon has more than 40 impact basins; many filled with magma and influenced the appearance of the lunar maria.
For scale, NASA’s guide describes Tycho as approximately 53 miles (85 km) across and 110 million years old. It calls Linné a young simple crater, thought to be less than 10 million years old, and 1.4 miles (2.2 km) wide. The guide’s retrieved page does not state a publication year for these figures.
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Note the direction of illumination and the shadows it casts. A bright or dark patch in one image is not by itself evidence of a fresh impact or unusual material. Compare the appearance with topography, elevation profiles and other available views or layers before drawing conclusions. When sharing an observation, identify the image or product and its metadata rather than assuming all tools show identical coverage, resolution or data.
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A new impact is a change over time, not simply a feature you have not seen before. MoonDiff is the tool in this workflow intended for comparing older and newer orbital images and finding candidate new craters.
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- Open MoonDiff and follow the project’s current comparison guidance.
- Compare the earlier and later views of the same location. Look for a new feature in the later image, not just a mark that is prominent under different lighting.
- Check for misleading changes. The project provides examples of red herrings—apparent differences that are not new impacts—so use those examples and the project’s instructions when assessing a candidate.
- Keep the claim appropriately cautious. Treat a suspected impact as a candidate unless the comparison and project guidance support identifying it as new.
MoonDiff also invites participants to look for missing spacecraft hardware. That is a separate search target from new craters, even though both rely on comparing images across time.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Use NASA maps and data when you want to go deeper
QuickMap is useful when you want to customize a view of LRO maps. NASA’s LRO Data Products page describes data products available through the Planetary Data System and LROC, including global, polar, regional, shapefile and topographic products. The Moon Trek and QuickMap interfaces are ways to explore lunar data; for a specific image or measurement, check the selected product’s metadata and source.
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NASA’s Investigating Impacts activity is a free way to practice finding and measuring named craters. A paper Moon atlas is optional if you prefer to keep a printed reference alongside the browser view; NASA’s crater guide and activity provide named examples, but do not endorse a specific atlas.
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