Final answer:
Earth appears brighter from Mars than vice versa due to Earth's higher albedo - reflecting more sunlight back into space - and its larger size.
Step-by-step explanation:
Earth would look brighter from Mars than Mars looks from Earth because Earth has a higher albedo, which is the measure of the reflectivity of a planet's surface. Earth reflects more sunlight due to its clouds and oceans compared to the rocky surface of Mars. Additionally, Earth is larger, which also contributes to its brightness when viewed from Mars.
The amount of sunlight reflected by a planet is an important aspect in astronomy called planetary brightness. The higher albedo of Earth means it reflects more sunlight, making it appear brighter in the Martian sky. To further understand this, one can consider the phase angle, which describes the angle at which the sunlight hits the planet as seen from Mars, and Earth, due to its various atmospheric and surface conditions, tends to reflect sunlight at a wide range of phase angles, leading to its increased brightness.