Final answer:
Mercury's highly eccentric orbit causes the precession of its perihelion, explained by Einstein's general theory of relativity, affecting the observed motion of the Sun from Mercury's surface.
Step-by-step explanation:
The main consequence of Mercury's highly eccentric orbit is the occurrence of a phenomenon known as the precession of the perihelion. Due to the gravitational perturbations from other planets and the significant warping of spacetime by the Sun's mass, each passage of Mercury at its closest point to the Sun (perihelion) shifts slightly in space. This effect was puzzling to astronomers until it was precisely explained by Einstein's general theory of relativity, which accounts for an additional 43 arcseconds of precession per century beyond that predicted by Newtonian physics. The eccentric orbit also leads to Mercury moving fastest in its orbit when it is nearest to the Sun, resulting in unusual motions of the Sun in the sky as observed from Mercury, especially within areas like Caloris Basin.