© NASA/Hubble Space Telescope

Mars enters retrograde motion

Dominic Ford, Editor
From the Outer Planets feed

Objects: Mars
Please wait
Loading 0/4
Click and drag to rotate
Mouse wheel to zoom in/out
Touch with mouse to dismiss
The sky at

Mars will enter retrograde motion, halting its usual eastward movement through the constellations, and turning to move westwards instead. This reversal of direction is a phenomenon that all the solar system's outer planets periodically undergo, a few months before they reach opposition.

The retrograde motion is caused by the Earth's own motion around the Sun. As the Earth circles the Sun, our perspective changes, and this causes the apparent positions of objects to move from side-to-side in the sky with a one-year period. This nodding motion is super-imposed on the planet's long-term eastward motion through the constellations.

The diagram below illustrates this. The grey dashed arrow shows the Earth's sight-line to the planet, and the diagram on the right shows the planet's apparently movement across the sky as seen from the Earth:

The retrograde motion of a planet in the outer solar system. Not drawn to scale.

2033 apparition of Mars

26 May 2033 – Mars enters retrograde motion
27 Jun 2033 – Mars at opposition
05 Jul 2033 – Mars at perigee
01 Aug 2033 – Mars ends retrograde motion

Observing Mars

Mars enters retrograde motion as its 2033 apparition gets underway, although it has already been visible for some weeks in the pre-dawn sky.

Its celestial coordinates as it enters retrograde motion will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 18h53m10s 25°19'S Sagittarius -1.6 17.4"

The coordinates above are given in J2000.0.

From Seattle , it will be visible in the morning sky, becoming accessible around 00:58, when it reaches an altitude of 7° above your south-eastern horizon. It will then reach its highest point in the sky at 03:45, 17° above your southern horizon. It will be lost to dawn twilight around 04:53, 15° above your southern horizon.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

Over the following weeks, Mars will reach its highest point in the sky four minutes earlier each night, gradually becoming visible in the evening sky, as well as the pre-dawn sky, as it approaches opposition.

The panels below show the month-by-month change in Mars' apparent size in coming weeks:

31 Mar 2033
28 Apr 2033
26 May 2033
23 Jun 2033
21 Jul 2033

The table below lists Mars' angular size at brightness at two-week intervals throughout its apparition:

Date Angular size Mag
17 Mar 20338.5”0.3
31 Mar 20339.6”0.0
14 Apr 203311.0”-0.3
28 Apr 203312.8”-0.7
12 May 203314.9”-1.2
26 May 203317.4”-1.6
09 Jun 203319.8”-2.1
23 Jun 203321.6”-2.5
07 Jul 203322.1”-2.5
21 Jul 203321.2”-2.2
04 Aug 203319.4”-1.9

The sky on 26 May 2033

The sky on 26 May 2033
Twilight ends
Twilight begins

27-day old moon
Waning Crescent


27 days old

Rise Culm. Set
Mercury 06:17 14:28 22:39
Venus 03:36 10:05 16:35
Moon 04:19 11:32 18:56
Mars 23:45 03:45 07:44
Jupiter 02:04 07:21 12:39
Saturn 07:21 15:14 23:08
All times shown in PDT.


The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

27 Jun 2033  –  Mars at opposition
05 Jul 2033  –  Mars at perigee
11 Sep 2035  –  Mars at perigee

Image credit

© NASA/Hubble Space Telescope






Color scheme