by MarkBour » Mon Oct 08, 2018 11:10 pm
MarkBour wrote: ↑Thu Oct 04, 2018 3:40 pm
I think opening a car wash would be a good business opportunity on Mars.
This MRO HiRise image shows some lovely long shadows. I wonder if I can figure out if it is from sunrise or sunset ...
Okay, so Wikipedia reveals:
https://en.wikipedia.org/wiki/Retrograd ... ade_motion
In our Solar System, the orbits about the Sun of all planets and most other objects, except many comets, are prograde, i.e. in the same direction as the Sun rotates. The rotations of most planets, except Venus and Uranus, are also prograde. Most natural satellites have prograde orbits about their planets. Prograde satellites of Uranus orbit in the direction Uranus rotates, which is retrograde to the Sun. Retrograde satellites are generally small and distant from their planets, except Neptune's satellite Triton, which is large and close. All retrograde satellites are thought to have formed separately before being captured by their planets.
So, that makes life pretty simple in most cases. For my question of the moment, if you get a satellite image looking down on a planet with the picture oriented so that North (Solar North, if you will) is up, then in most cases what happens is similar to Earth. On Mars, the Sun will also rise in the East and set in the West. So in this image, if North is up, then we are looking at lengthening shadows and it must be nearing sunset.
[quote=MarkBour post_id=286303 time=1538667643 user_id=141361]
I think opening a car wash would be a good business opportunity on Mars.
This MRO HiRise image shows some lovely long shadows. I wonder if I can figure out if it is from sunrise or sunset ...
[/quote]
Okay, so Wikipedia reveals:
[quote][url]https://en.wikipedia.org/wiki/Retrograde_and_prograde_motion[/url]
In our Solar System, the orbits about the Sun of all planets and most other objects, except many comets, are prograde, i.e. in the same direction as the Sun rotates. The rotations of most planets, except Venus and Uranus, are also prograde. Most natural satellites have prograde orbits about their planets. Prograde satellites of Uranus orbit in the direction Uranus rotates, which is retrograde to the Sun. Retrograde satellites are generally small and distant from their planets, except Neptune's satellite Triton, which is large and close. All retrograde satellites are thought to have formed separately before being captured by their planets.[/quote]
So, that makes life pretty simple in most cases. For my question of the moment, if you get a satellite image looking down on a planet with the picture oriented so that North (Solar North, if you will) is up, then in most cases what happens is similar to Earth. On Mars, the Sun will also rise in the East and set in the West. So in this image, if North is up, then we are looking at lengthening shadows and it must be nearing sunset.