If you lived on Mars, which planets would describe retrograde loops? Which would never be visible as crecent phases?
Retrograde motion for outer (Jupiter and beyond); crescent phases for inner (Earth, Venus and Mercury).
N/m I figured it out.
If you were living on Mars, you would observe retrograde loops in the motions of the outer planets—Mars being an inner planet itself. Retrograde motion refers to the temporary apparent reversal of a planet's path in the sky.
From Mars, the outer planets that would exhibit retrograde loops are:
1. Jupiter: Jupiter experiences retrograde motion approximately once every 13 months.
2. Saturn: Saturn goes through retrograde cycles approximately once every 12 months.
3. Uranus: Uranus has a regular retrograde cycle occurring once every 84 years.
4. Neptune: Neptune experiences retrograde motion roughly once every 165 years.
Regarding crescent phases, you would not observe them for the outer planets from Mars. Crescent phases are only visible for inner planets (Mercury and Venus) when observed from Earth or other inner planets. Since outer planets like Jupiter, Saturn, Uranus, and Neptune are always located further away from the Sun than Mars, they will never exhibit crescent phases when observed from Mars.
To determine which planets would exhibit retrograde loops and which would never be visible as crescent phases, we need to understand the concept of these phenomena and the orbital characteristics of the planets in our solar system.
1. Retrograde Loops:
Retrograde motion refers to the apparent backward motion of a planet in its orbit when observed from Earth. It occurs because of differences in the orbital speeds of the Earth and the planets. To identify which planets exhibit retrograde loops when viewed from Mars, we can use Earth as a reference point.
From Earth, only two planets display retrograde loops: Mars and Saturn. Mars itself goes through retrograde motion when observed from Earth, whereas Saturn displays retrograde motion because of its slower orbital speed compared to Earth.
Therefore, if you were living on Mars, the only planet that would exhibit a retrograde loop would be Saturn, as viewed from Mars.
2. Crescent Phases:
Crescent phases occur when planets are positioned in such a way that only a small portion of their illuminated side is visible from a specific point, such as Earth or Mars. To ascertain which planets never appear as crescent phases when observed from Mars, we need to consider their positions relative to Mars and the Sun.
From Mars, the four inner planets (Mercury, Venus, Earth, and Mars itself) will exhibit crescent phases since they can be positioned between Mars and the Sun at various points in their orbits.
Neptune and Uranus, being outer planets, are always positioned outside Mars' orbit; hence, they will not show crescent phases from Mars.
However, it is worth noting that Jupiter and Saturn may exhibit crescent phases infrequently, as their positions can be between Mars and the Sun during certain conjunctions. But this occurrence is rare and not frequently observable.
In summary, from Mars, the planets that will exhibit crescent phases are Mercury, Venus, Earth, and Mars. The outer planets (Jupiter, Saturn, Uranus, and Neptune) will not show crescent phases, except for rare instances with Jupiter and Saturn.