Mars Retrograde Loops 1978 - 2040

The purpose of this page is to illustrate the changing nature of the retrograde loops executed by Mars at each of its oppositions from 1978 (in the Cancer direction) to 2040 (in Gemini).  We can see that when Mars is in the Gemini - Cancer - Leo part of its orbit, the retrograde loops are all north of the ecliptic, which is an indication that Mars is above the plane of the ecliptic during those times.  Conversely, when Mars is in the Sagittarius - Capricornus - Aquarius part of the sky, those retrograde loops are downward because Mars' orbit is below the ecliptic plane then.

Another interesting feature of Mars' orbit that we can see from the shape of the loops is that when Mars is at aphelion, which therefore means that the opposition is relatively distant, the retrograde loops are long.  When opposition occurs in the July - August - September timeframee, however, the loops are shorter because Mars is around perihelion during those oppositions.  The symmetrical S-shaped patterns in Libra and Aries occur when the opposition coincides with Mars being near its descending and ascending nodes, respectively.  All of these characteristics and relationships are clearly explained and brilliantly diagrammed on Guy Ottewell's website; other excellent resources for insight into Mars' orbit are at Jürgen Giesen's site, EarthSky.Org, the always excellent graphics at In the Sky.Org, Naked Eye Planets, Professor Seligman's site, and one of my favorite collections of diagrams, the Mars page at Stjerneskinn.com.

The diagrams around the periphery expand when you mouse-over them, and to keep the image displayed, move the mouse over the expanded image.  The top left corner is 1978, and the dates go around clockwise until you reach 2040 directly underneath 1978.  We can begin to see some of the larger patterns among Mars oppositions, the first of which is the grouping of opposition series' into even and odd year sets, most of which comprise 7 apparitions, occasionally 8 (such as 1993 - 2007).  As an extension of that pattern is the 15 to 17 year cycle between similar oppositions of succeeding series, such as 1993 - 1978 = 15, or 2010 - 1993 = 17, or 2025 - 2010 = 15 years.  I have enough examples here on the page to highlight another somewhat close pattern, namely the 47 year "kinda close" repetition of oppositions, such as 2025 - 1978 = 47 years (the dates were January 21, 1978 and January 16, 2025.  A closer repetiion would be the 2057 opposition, which is 79 years beyond 1978.  The date of opposition in events 79 years apart differs by only three days.

Adding interest to a Mars opposition is proximity to Jupiter or Saturn also near opposition ~ this happened in 1980, 1982, 1984, 2016, and will happen again in 2027 and 2029.  Nice!  Mars' Size at Opposition, Back to Mars Oppositions, Back to Starvergnügen.

  According to a google search, the Moon's albedo is 0.12, whereas the albedo of Mars is 0.17.  I could not detect a significant difference in the surface brightness of the two bodies, and in fact I would say that they appeared to be very similar as the Moon approached Mars ~ maybe the difference is that the Moon's albedo must be an average of the reflectivity of the bright highland areas and the darker mare regions.  As the two grew closer, it was Mars being juxtoposed against a brighter, whiter region of the Moon.  The actual occultation took less than a minute, at least that's the way it seemed to me.
 
The main features on the Moon that we are seeing approach Mars are the famous ray crater Tycho on the right side of the pictures, and left of the center of the Moon are the ray craters Copernicus and Kepler (top and bottom, respectively).  Between Tycho on the right and Copernicus and Kepler on the left are the two smaller mare, Nubium above and Humorum below.  The large dark area below and to the left of Copernicus / Kepler is Oceanus Procellarum.  The bright spot to the lower left of Kepler is Aristarchus.