[Chris]

Chris asked the Naked Scientists:
   
Ignoring the why and how. What are the ramifications of moving Mars into the Earths orbit lagged 180 degrees?

Keep up the excellent work
Chris of Cardiff

What do you think?

[Vern]

Lagged by 180 degrees would put it always behind the sun. Since Mars is less massive than Earth, I don't know if there is a solution to the Sol Mars orbit that would place it always behind the sun. But I haven't plugged in the numbers to know.

If it could stay directly behind the sun, we would probably not know it. We would need to send an expedition to discover it.

[Soul Surfer]

This is not a stable position for any object to orbit for a long period unless it is deliberately maintained in this position by tie expending of energy.

The reason for this is as follows the ellipticity of the earth's orbit and or interactions with the gravitation of other bodies in the solar system like Jupiter would move it away from the unstable equilibrium point and then the mutual attraction would cause the earth and Mars to interact.  There is a natural moon of the earth that follows this orbit which can be stable for a low mass object.(see the thread on how many moons does the earth have)  The most stable place another object to orbit with the earth is 60 degrees in advance or 60 degrees behind the earth ie forming an equilateral triangle between the sun the earth and the third body.  It might be possible to put Mars there and have the system stable for a long period.  In that case it would appear as a bright red star in the sky a bit like Venus always appearing in exactly the same position before sunrise or after sunset according to which side of the earth you put it.

[lyner]

It is possible for a second body to orbit, equidistant from the Sun. It's called a Trojan or Horseshoe orbit but is only stable for a very small object.
Look at this link (and several others) ...sorry, you cannot view external links. To see them, please REGISTER or LOGIN.
There are Trojan Asteroids which share Jupiter's orbital distance.

[syhprum]

This planet was first observed in 1969 as recorded in the film Doppelganger

...sorry, you cannot view external links. To see them, please REGISTER or LOGIN

[Vern]

There was a similar one in the series Star Track some years back.