The upper chart shows the path of Mars across the background stars over the course of the year. Stars to magnitude +4.5 are shown with some fainter objects included to complete constellation patterns. The white circles represent the planet on the first day of the month and are scaled according to apparent magnitude. The faint paths before the first circle and after the last circle represent the planet's positions in December of last year and January of next. In general, the planet moves from right to left except when it's in retrograde and proceding in the opposite direction.
The lower chart shows how the appearance of Mars changes over the year. Below each image is listed the date, the apparent magnitude, the apparent diameter of the disk (in arc-seconds), the geocentric distance (in au) and the percentage of the disk which is illuminated. Note that Mars appears distinctly gibbous near the times of quadrature.
With neither opposition nor retrograde motion happening this year, Mars proceeds in an orderly fashion across the sky, beginning as a bright zero magnitude object in Pisces before dimming to second magnitude by the middle of the year. It recovers its brightness slightly and ends up at magnitude +1.5 in Ophiuchus. Mars is an evening sky object at the outset of 2021, visible before sunset for the first half of the year. Conjunction is in October, after which the red planet reappears in the east at dawn. Mars is occulted by the Moon three times this year (April and December) and passes just south of the open star cluster Praesepe in late June. Its closest appulse with another planet occurs in August when Mercury appears just 0.1° south of Mars.
| 05 January | Pisces → Aries |
| 20 January | planetary conjunction: 1.6° north of Uranus |
| 01 February | east quadrature |
| 07 February | equinox: spring in the northern hemisphere and autumn in the southern hemisphere |
| 23 February | Aries → Taurus |
| 19 March | 1.9° north of the Moon |
| 17 April | lunar occultation: 0.1° north of the Moon |
| 23 April | maximum declination north |
| 24 April | Taurus → Gemini |
| 07 May | stellar occultation: HD 47020 |
| 16 May | 1.5° south of the Moon |
| 08 June | Gemini → Cancer |
| 13 June | 2.8° south of the Moon |
| 23 June | 0.3° south of the open star cluster M44 (known as Praesepe or the Beehive Cluster) |
| 10 July | Cancer → Leo |
| 13 July | aphelion |
| planetary conjunction: 0.5° south of Venus | |
| 29 July | 0.6° north of Regulus |
| 19 August | planetary conjunction: 0.1° north of Mercury |
| 25 August | solstice: summer in the northern hemisphere and winter in the southern hemisphere |
| 05 September | Leo → Virgo |
| 08 October | conjunction |
| 09 October | planetary conjunction: 2.4° north of Mercury |
| 04 November | 2.3° south of the Moon |
| 10 November | planetary conjunction: 1.0° south of Mercury |
| 11 November | Virgo → Libra |
| 02 December | lunar occultation: 0.7° south of the Moon |
| 15 December | Libra → Scorpius |
| 19 December | descending node |
| 24 December | Scorpius → Ophiuchus |
| 31 December | lunar occultation: 0.9° north of the Moon |
| maximum declination south |
