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Draw a Mars Disk with Surface Feature Shading
Learn to draw a Mars disk with polar caps, dark albedo features, limb darkening, and a soft terminator using a simple tonal convention and checkable geometry.
Free lesson
Four exercises
Worked answers
Object Drawing Lessons
This lesson teaches a repeatable method for drawing a Mars disk with believable surface-feature shading. You will set a circle, place polar caps and dark albedo patches, then build tone from the limb inward and soften the terminator. The convention is explicit: x-height means the vertical distance from baseline to midline of a lowercase letter in your normal handwriting, and all letter styles are acceptable as long as that distance is measured consistently. Numerical values below are hypothetical examples; measure your own paper and tools before committing to them.
Practice materials: Printable downloads are not available for this lesson yet. Use the instructions and four exercises below.
Set the disk and the tonal convention
Begin with a circle drawn lightly. Mark its center and a vertical axis. Decide a shading convention before adding features: use three tones only, light, mid, and dark, and define what each means on your paper. For example, light may be the untouched paper, mid may be one even layer of pencil, and dark may be two crossed layers. Keep the same pressure and pencil throughout so the tones remain comparable.
Measure your equipment rather than assuming standard sizes. If your circle diameter is 80 mm, a polar cap of about 8 mm depth is a hypothetical starting point; adjust after checking how the cap reads at viewing distance. Record the actual diameter and cap depth on the page margin so later checks use real numbers.
- Draw a light circle and mark center and vertical axis.
- Write your three-tone key in a corner: light, mid, dark.
- Measure the circle diameter with a ruler and note it.
- Choose a hypothetical cap depth, such as one tenth of the diameter, and mark it lightly.
Place polar caps and dark albedo features
Polar caps sit at the top and bottom of the disk. Draw each as a shallow curved band inside the circle, not as a flat line across it. The cap edge should curve with the disk so it reads as lying on a sphere. Keep the cap tone light and leave a thin unshaded rim at the very edge to suggest the limb.
Dark albedo features are irregular patches, not geometric shapes. Place two or three elongated patches across the middle latitudes, angled slightly with the disk curvature. Use the mid tone first, then add dark only where the feature is strongest. Avoid covering the center completely; leave light gaps so the disk does not look like a flat sticker.
- Draw the upper cap as a curved band and the lower cap smaller if you choose.
- Block two or three elongated dark patches with light outlines.
- Fill patches with mid tone, then strengthen centers with dark.
- Leave light gaps between patches and a thin rim at the limb.
Build limb darkening and a soft terminator
Limb darkening means the edge of the disk is slightly darker than the center. Add a narrow band of mid tone just inside the circle, following the curve. Keep the band even and no wider than about one twentieth of the diameter as a hypothetical guide. This band should not touch the polar caps; leave a light gap so the caps stay readable.
The terminator is the boundary between lit and unlit sides. Choose one side as shadowed and shade from the terminator outward with mid tone, then dark near the outer edge. Soften the terminator by light hatching or blending so it is a gradual zone, not a hard line. Check that the shadow does not erase the dark albedo features entirely; they should remain visible as darker shapes within the shadow.
- Add a narrow mid-tone band inside the limb all around.
- Mark a terminator curve on one side with a light line.
- Shade from terminator outward, increasing tone toward the edge.
- Soften the terminator and confirm features remain visible.
Check geometry and tone before finishing
Use simple arithmetic to check placement. If the diameter is 80 mm, the radius is 40 mm. A cap depth of 8 mm is one tenth of the diameter and one fifth of the radius. A limb band of 4 mm is one twentieth of the diameter. These are hypothetical examples; substitute your measured values and confirm each proportion by division.
Check tone by stepping back. The lightest area should be the cap or a gap between features, the mid tone should dominate the disk, and the dark should be limited to feature cores and the shadow edge. If the disk looks flat, add a little more mid tone near the limb; if it looks muddy, lift tone with an eraser in the light gaps.
- Measure diameter, radius, cap depth, and limb band width.
- Divide to confirm proportions match your plan.
- Step back and rank the three tones from lightest to darkest.
- Adjust one area only, then recheck.
Worked example
A circle has a measured diameter of 60 mm. You plan a cap depth of 6 mm and a limb band of 3 mm. Confirm the proportions and describe where to place two dark patches.
Worked answer
Radius is 30 mm. Cap depth 6 mm is one tenth of the diameter and one fifth of the radius. Limb band 3 mm is one twentieth of the diameter. Place one elongated dark patch across the upper middle latitude and one across the lower middle latitude, leaving a light gap at the center and a thin light rim at the limb. Shade the limb with a 3 mm mid-tone band, then add a soft terminator on one side.
Four practice exercises
Exercise 1
A circle has a measured diameter of 100 mm. You choose a cap depth of 10 mm and a limb band of 5 mm. State the radius and confirm each proportion by division.
Show answer and check
Radius is 50 mm. Cap depth 10 mm is one tenth of the diameter and one fifth of the radius. Limb band 5 mm is one twentieth of the diameter.
Why: Divide diameter by two for radius. Divide cap depth by diameter and by radius. Divide limb band by diameter. All divisions use the same units, millimetres.
Check: Recompute each division with a calculator or by hand and confirm the results match the stated fractions.
Exercise 2
A disk of diameter 80 mm has a terminator drawn as a hard straight line on the left side. Describe two changes that would make the terminator read as a soft zone and explain how to check the result.
Show answer and check
Replace the straight line with a curved boundary that follows the disk, and soften it with light hatching or blending so tone increases gradually toward the edge. Check by stepping back: the transition should be a zone, not a line, and dark features should remain visible.
Why: A terminator on a sphere curves with the disk. A hard line reads as flat. Softening creates a gradual tonal change. The check is visual and does not require new measurements.
Check: View the drawing at arm's length and confirm no sharp line separates lit and shadowed areas.
Exercise 3
You have placed three dark patches but the disk looks flat. Using only the three-tone key, describe one adjustment and one check.
Show answer and check
Add a narrow mid-tone band inside the limb, keeping it even and no wider than one twentieth of the diameter as a hypothetical guide. Check by ranking the tones: lightest at cap or gaps, mid dominant, dark limited to feature cores and shadow edge.
Why: Flatness often comes from missing limb darkening. A narrow mid-tone band adds curvature without changing feature placement. The tone ranking confirms the key is still respected.
Check: Step back and list the lightest, middle, and darkest areas; confirm they match the key.
Exercise 4
A circle of diameter 70 mm has a cap depth of 7 mm. A classmate says the cap is too deep because it is one fifth of the radius. Check the arithmetic and state whether the claim is correct.
Show answer and check
Radius is 35 mm. Cap depth 7 mm is one tenth of the diameter and one fifth of the radius. The arithmetic is correct, but whether the cap is too deep is a visual judgement, not an arithmetic error.
Why: Divide 70 by 2 to get 35. Divide 7 by 70 to get one tenth. Divide 7 by 35 to get one fifth. The claim about the fraction is right; the judgement about depth needs a visual check.
Check: Recompute the divisions and then view the drawing at arm's length to judge cap depth.
Common mistakes
- Drawing polar caps as straight lines across the disk. Curve each cap edge to follow the circle so it reads as lying on a sphere.
- Making dark albedo features too geometric or too large. Use irregular elongated patches and leave light gaps between them.
- Shading the limb with a hard, wide band. Keep the limb band narrow and even, and blend its inner edge.
- Letting the terminator become a sharp line. Soften the terminator with light hatching or blending so it is a gradual zone.
- Using inconsistent pencil pressure so tones cannot be compared. Define a three-tone key first and keep the same pressure throughout.
Self-check rubric
- Disk is a light circle with center and vertical axis marked.
- A three-tone key is written and used consistently.
- Polar caps are curved bands inside the circle, not straight lines.
- Two or three irregular dark albedo patches are placed with light gaps.
- Limb darkening is a narrow even band that does not touch the caps.
- Terminator is softened and features remain visible within the shadow.
- Measured diameter, cap depth, and limb band are recorded and checked by division.
- Valid alternatives are accepted if the convention is stated and the geometry checks out.
Questions and answers
Do I need a perfect circle?
A lightly drawn circle is enough. Check it by measuring two diameters at right angles; if they differ by more than a small amount, redraw lightly.
How dark should the dark albedo features be?
Dark enough to read as the strongest surface tone but not so dark that they merge with the shadow edge. Use your three-tone key as the limit.
Can I use any letter style for the x-height convention?
Yes. Any letter style is acceptable as long as you measure baseline to midline consistently and record the value you used.
What if my measured proportions differ from the hypothetical examples?
Use your measured values. The examples are only starting points; the check is whether your divisions are consistent with what you drew.