Question

What piece of evidence suggests that the Martian moons did NOT form with Mars?

A: They have circular orbits above the Martian equator.
B: They have ages that are much younger than Mars.
C: Their composition is significantly different from Mars and the terrestrial planets.
D: They are both irregularly shaped and are heavily cratered.
E: They rotate synchronously, with one side tidally fixed toward Mars.

Answer 1

The Martian moons Phobos and Deimos likely did not form with Mars since their composition and irregular, asteroid-like structure indicate they were likely captured asteroids, differing significantly from the composition of Mars and the terrestrial planets.

Step-by-step explanation:

The piece of evidence suggesting that the Martian moons did not form with Mars is C: Their composition is significantly different from Mars and the terrestrial planets. This conclusion is drawn from observations made by various missions such as the Viking orbiters and the Mars Global Surveyor. These missions have shown that Phobos and Deimos are irregular, somewhat elongated, and heavily cratered, resembling other smaller asteroids, rather than the usual spherical moons formed with their planets.

Their structure does not resemble the volcanic basalts found in Martian meteorites, which are known to originate from Mars. Instead, their characteristics suggest that these moons were probably captured asteroids, similar to the small outer moons of Jupiter and Saturn.