Mars orbits outside Earth’s orbit, so it is a superior planet. The lesson is not a crescent. It is where Mars sits relative to the Sun. Opposition puts Earth in the middle — Sun, Earth, Mars in a line — so Mars is opposite the Sun in the sky. On a classroom cartoon that means it rises around sunset and stands highest near midnight. Conjunction puts the Sun in the middle: Mars is on the far side, near the Sun, and hard to see. Quadrature is the right angle at Earth, east or west, midway in angle between those lineups. Venus does not do this. Venus is an inferior planet; its extremes are elongations, on the Venus desk. The backward loop around opposition is Earth lapping Mars, on the retrograde desk — the orbit does not reverse. Pair it with the solar map (where the planets sit) and with gravity, the pull that keeps both worlds on their tracks.
Educational schematic — circular orbits, flattened onto one plane, disks exaggerated so a phone can see them. Earth is held on the right so the angle at Earth is easy to read. The Mars marker walks clockwise on that frozen view because Earth is the faster world; the orbit arrows stay counterclockwise. Circle radii use the semimajor-axis ratio on NASA’s Mars Fact Sheet, 1.524. That sheet lists Mars’s eccentricity as 0.0935 and its orbit inclination as 1.848°. Not an ephemeris. Not a date of the next Mars opposition. Not for pointing a telescope from Campbell or anywhere else. This cartoon does not print magnitudes.
Interactive · Top-down
North up · Earth held on the right · orbit arrows still counterclockwise
As seen from Earth · toward the Sun, or opposite it · cartoon, not a chart
Sun
Earth · inner, faster
Mars · outer / superior
Angle at Earth
0 d
Literacy · words for the lineup
Opposition
NASA’s Basics of Space Flight: Earth and the outer planet on the same side of the Sun, all three in a line. The Moon, when full, is in opposition to the Sun; Earth is then approximately between them. The chapter calls opposition a good time to observe, because the planet is nearest and in its fullest phase. A 2020 NASA sky note describes that lineup from the ground: Mars rises at sunset and is high around midnight, and looks larger and brighter because it is closer. The miles, “third brightest,” and the 2035 date on that page belong to October 2020. This slider does not print a magnitude. Mars’s eccentricity on the fact sheet is 0.0935, so a real closest approach can miss the instant. These circles do not time it. The loop around the passing is the retrograde desk.
Conjunction
For a superior planet, only a superior conjunction. Basics of Space Flight: Earth and the planet on opposite sides of the Sun, nearly in a straight line, Sun between. The planet passes closest to the Sun as seen from Earth. The 2020 note’s contrast is the far one: Mars and Earth are far apart, so Mars appears small and faint. That is not Venus’s inferior conjunction, where the planet sits between Earth and the Sun. Venus never reaches opposition in this sense. Its desk is elongations.
Quadrature
The right-angle case. A NASA GSFC ephemeris preface maps solar elongation like this: 0° is solar conjunction, 90° east is eastern quadrature, 180° is opposition, and 90° west is western quadrature. Eastern elongations place the planet in the evening sky; western elongations place it in the morning sky. On these circles the Sun–Earth–Mars angle is 90° at those two presets. The degree on the panel is the cartoon, drawn from the 1.524 ratio. The space-flight chapter names opposition and conjunction; it does not use the word quadrature, so this desk does not pretend that it does.
Synodic period
The repeat of the same Sun–Earth–Mars alignment. The Mars Fact Sheet lists it as 779.94 days. Sidereal orbit periods on that sheet are 686.980 days for Mars and 365.256 days for Earth. The 2020 sky note says oppositions happen about every two years and two months. This slider counts 779.94 days instead of turning that phrase into a new figure. It does not name the next opposition over Campbell.
Superior planet
Basics of Space Flight: Mars, Jupiter, Saturn, Uranus, and Neptune are superior planets because their orbits are farther from the Sun than Earth’s, not because they rank higher. They usually appear gibbous, and full at opposition; at superior conjunction the chapter says the outer planet appears near its fully illuminated phase, still lost near the Sun. Inferior planets — Mercury and Venus — can never be at opposition from Earth’s point of view. Their apparent angle from the Sun is an elongation. That lesson is the Venus desk. This drawing uses Mars as the outer planet. The same lineup words apply to the other superior planets; the circle ratio here is Mars’s.
Bright, on a cartoon
Closer on these circles is opposition. Farther is conjunction. The 2020 NASA note says the near pass looks larger and brighter, and the far lineup looks small and faint. NASA’s January 2025 Night Sky Notes say Mars increases in brightness as it reaches opposition, and that opposition is when a planet is directly opposite the Sun. The fact sheet also lists an apparent visual magnitude and a maximum apparent visual magnitude. Those are not a position on this slider, so they are not printed. No magnitude, no arcseconds, and no “next opposition” date.
Sources · public NASA education
Cited, not invented
NASA Science — Basics of Space Flight, Chapter 1 — Mercury and Venus are inferior planets because their orbits are closer to the Sun than Earth’s; Mars through Neptune are superior planets because their orbits are farther out. Superior planets usually appear gibbous and appear full at opposition. They have only superior conjunctions: Earth and the planet on opposite sides of the Sun. At superior conjunction the outer planet appears near its fully illuminated phase. Opposition puts Earth and the outer planet on the same side of the Sun, all three in a line — the same word as a full Moon, with Earth approximately between. Opposition is a good time to observe because the planet is nearest and in its fullest phase. Inferior planets can never be at opposition from Earth’s point of view.
NASA NSSDCA — Mars Fact Sheet — semimajor-axis ratio 1.524; sidereal orbit periods 686.980 days (Mars) and 365.256 days (Earth); synodic period 779.94 days; mean orbital velocity 24.08 km/s (Mars) and 29.78 km/s (Earth); eccentricity 0.0935; inclination 1.848°. Those means set the circles. They are not a nightly position. The sheet’s apparent visual magnitude, maximum apparent visual magnitude, and apparent diameter are not printed on this slider.
NASA GSFC — Twelve Year Planetary Ephemeris, preface — solar elongation runs from 0° to 180°, east or west of the Sun. Eastern elongations place the planet in the evening sky; western elongations place it in the morning sky. Elongations of 0°, 90° east, 180°, and 90° west correspond to solar conjunction, eastern quadrature, opposition, and western quadrature.
NASA — It’s All About Mars in October (2020) — at opposition Earth passes near Mars, which is easily visible and bright; at conjunction Mars and Earth are far apart, so Mars appears small and faint. Because the Sun, Earth, and Mars are lined up, Mars rises at sunset and is high overhead at midnight, and proximity makes it appear larger and brighter. The miles, the “third brightest” ranking, and the September 2035 date on that page are that season, not this slider. The page’s “about every two years and two months” is not converted into a day count here.
NASA Science — January’s Night Sky Notes: The Red Planet — opposition is when a planet is directly opposite the Sun as seen from Earth; Mars increases in brightness approaching that opposition, and it is also when Mars is closest to Earth. The December 2024–February 2025 dates on that page belong to that season.
Classroom picture of an outer planet opposite the Sun, then lost near it. Not an ephemeris, not a pointing aid, and not a Campbell observing plan. Days on the slider are a coordinate of these circles, counted from a schematic opposition. The angle is the Sun–Earth–Mars angle on the cartoon. Separation is the distance between the circle points, in Earth-circle units, from the fact sheet’s 1.524 ratio — not a published range to Mars. Periods and that ratio are the ones NASA publishes on the pages above. This cartoon does not print magnitudes. Earthrise preview: NASA / Bill Anders (public domain).