View Full Version : Mars Trojans

2007-Aug-14, 10:47 PM
A new asteroid 2007NS2 was found last 14/07/2007 .
This one shares an orbit with Mars in the L5 point . It brings the known number of Trojans to 4 . 2 others share the point L5 , while another is in the L4 point . Herunder is the link for the list of those asteroids
A simulation of this 4 asteroids in a rotating frame with Mars gives the following picture :
The new one 2007NS2 is the light green orbit . Mars is represented as the "line" at the bottom of the picture .
There are a few astonishing features here : look at the unusual orbit of the green asteroid at the left , also the orbit at the right doesn't represent a kindney bean .
Remarkable also is the fact that the concave side of the left asteroids is once away from the sun and once directed to the sun .

Data were taken from the Nasa Near Earth Orbit Program .
More information about this simulation can be found on :

2007-Aug-15, 07:21 PM
When I clicked on the simulation, it looked like you were in an inertial frame, looking down at the solar system from above.

From the Wiki definition of Trojan asteroids: http://en.wikipedia.org/wiki/Trojan_asteroid

The Trojan asteroids are a large group of objects that share the orbit of the planet Jupiter around the Sun. Viewed from a coordinate system that is fixed on Jupiter, they appear to orbit one of the two Lagrangian points of stability, L4 and L5, that lie 60 ahead of and behind Jupiter in its orbit. They have semi-major axes between 5.05 AU and 5.40 AU, and lie in elongated, curved regions around the two Lagrangian points. They are called 'Trojans' because of a convention whereby they are named after characters from the Trojan War.
The term 'Trojan' is sometimes used to refer to other small solar system bodies that have similar relationships to other major bodies: for example, there are Mars Trojans and Neptune Trojans.

So, I take it that the green orbits in your simulation were the orbits of the asteroids around the Lagrangian points near Mars' orbit.

How stable are these orbits? Wouldn't normal precession of Mars' orbit disrupt these Trojans' orbits after a period of time?

2007-Aug-15, 07:40 PM
Moved from General Science to Astronomy.

2007-Aug-15, 08:05 PM
The simulation was done in a rotating frame with Mars . So the orbits are relative to the Mars motion . The picture was indeed taken from above .
The program in the link is quite well suited to simulate such thing s.
About the stability : asteroids of this kind of orbit seem stable within "short" periods of time , let us say 1 million years (10^6 ).

2007-Aug-15, 08:23 PM
To be more precise : the Mars orbit is shown in this frame as the straight line at the bottom . The other orbits from the innerside are : Sun (center ) , Mercury , Venus and Earth ( red dotted lines ) . Due to the post the picture is not tjat clear . To get a better picture I suggest that you use the lastlink in the article.