Use NASA’s browser-based Moon Trek or LROC QuickMap to find and inspect craters already mapped on the Moon. To investigate whether a crater is genuinely new, compare orbital images from different dates with MoonDiff: a feature that is unfamiliar in one view is not proof of a recent impact.
Choose the right NASA tool for your goal
| Tool | Best for | What it offers |
|---|---|---|
| Moon Trek | Guided exploration and measuring surface features | NASA describes 3D flyovers and analysis using spacecraft data. Its About page describes feature search, data layers and downloads, metadata, distance measurement, elevation plots, lighting, and slope analysis. The About page reported version 3.6.29 when accessed; interface details may change. |
| LROC QuickMap | Custom map exploration using Lunar Reconnaissance Orbiter maps | NASA describes QuickMap as a web mapping and analysis interface for LRO lunar maps. NASA’s LRO data-products page lists global, polar, regional, shapefile, and topographic products. |
| MoonDiff | Checking for possible new impacts | The project invites citizen scientists to compare older and newer orbital images for new craters and missing spacecraft hardware, and provides examples of apparent changes that are misleading. |
For a first crater search, Moon Trek is a practical starting point because NASA’s activity demonstrates a search-and-measure workflow. QuickMap is useful when you want to explore LRO map products. Use MoonDiff when the question is whether something changed between image dates. Do not assume the tools show identical coverage, resolution, or data; check the displayed source and metadata for the view you use.
Find a named crater in Moon Trek
NASA’s free classroom activity, “Investigating Impacts,” demonstrates how to locate and measure craters. Its interface descriptions may not match every current screen exactly, but the core sequence is straightforward.
- Open NASA Moon Interactives and launch Moon Trek.
- Choose a view, such as 3D Globe, North Pole Map, Global Map, or South Pole Map. Zoom and pan to the region you want to inspect.
- Enable the Nomenclature feature or layer so named lunar features are labeled. Interface positions can change, so look for the layer or feature controls rather than relying on a fixed button location.
- Search for a named crater. NASA’s activity uses Dawes as its example and suggests repeating the exercise with Moltke, Tycho, Copernicus, Clavius, and Theophilus.
- Record the displayed data source and metadata for the view. Those details matter when describing what a measurement represents.
Measure a crater and inspect its profile
Moon Trek’s measurement tools can help describe a feature, but the result depends on the displayed data and where you place each line. Treat an on-screen reading as a measurement of that view, not automatically as a new scientific result.
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- Diameter: Use the line tool across the widest rim-to-rim span.
- Circumference: Trace around the crater’s edge with the polyline tool.
- Cross-section: Draw a profile line from outside one rim, across the crater, and beyond the opposite rim. Inspect the resulting elevation profile to compare rim, floor, and surrounding terrain.
For a careful description, note the image or data layer, the line placement, and the viewing conditions. Compare the image with topography where available: shadows and illumination can change how a rim, floor, or bright and dark patch appears.
Read crater shape without over-interpreting it
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 diameter alone is not a complete interpretation.
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Simple and complex craters
NASA describes simple craters as relatively small, smooth, bowl-shaped features with round floors, typically no more than around 6–9 miles (10–15 km) across. Complex craters are generally around 9 miles (15 km) or more and can have central peaks, terraces, and flatter floors. Because those size ranges meet at the boundary, do not classify a crater from diameter alone; inspect its shape and topography as well.
Basins and named examples
NASA’s crater guide describes lunar basins as impact structures more than 186 miles (300 km) across and reports more than 40 on the Moon. Many filled with magma and influenced the appearance of the lunar maria. The same guide gives Tycho as approximately 53 miles (85 km) in diameter and 110 million years old, and Linné as a young simple crater thought to be less than 10 million years old and 1.4 miles (2.2 km) wide. NASA’s page does not expose a publication year for these figures.
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Lighting and apparent changes
Shadows depend on illumination, so a single image may make terrain look different from another view. A bright or dark patch alone does not establish a fresh impact or unusual material. Compare views and data layers, and use image metadata to understand what you are looking at.
How to check whether a crater is new
A newly formed crater is a claim about change over time. Use MoonDiff to compare older and newer orbital images rather than relying on a crater’s unfamiliar appearance in a static map.
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- Open MoonDiff and follow the project’s image-comparison guidance.
- Compare the older and newer views of the same area, looking for a feature that appears in the later image but not the earlier one.
- Check whether the apparent difference could be explained by lighting, image conditions, or other changes in the views. MoonDiff includes examples of red herrings.
- Keep an observation as a candidate unless the comparison and project guidance support identifying it as a new crater.
Practice with NASA’s activity or a paper atlas
The free NASA “Investigating Impacts” activity provides a structured way to practice finding and measuring named craters. A printed Moon atlas can be a useful optional companion if you prefer a paper reference for feature names, but it is not required to explore NASA imagery. NASA’s crater guide and activity do not endorse a particular atlas.
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