Europa, one of Jupiter’s four largest moons, holds immense scientific interest due to strong evidence suggesting a vast, subsurface saltwater ocean. This ice-covered world, discovered by Galileo Galilei in 1610, is a prime target in the search for potential extraterrestrial habitats. Comparing its dimensions, bulk, and location to Earth helps fully appreciate the Jovian moon.
Comparing Linear Dimensions
Europa is dramatically smaller than Earth, possessing a diameter of approximately 3,100 kilometers (1,940 miles). Earth, by comparison, has an average diameter of about 12,742 kilometers (7,918 miles). This means Europa is roughly one-quarter the linear size of our home planet.
The Jovian moon is also slightly smaller than Earth’s own Moon, measuring about 90% of its diameter. Its circumference is around 9,800 kilometers (6,094 miles), which is only slightly more than the distance to cross the continental United States.
Relative Bulk and Gravity
The difference in bulk, or mass, between Europa and Earth is pronounced. Europa has only about 0.008% of Earth’s total mass. This low mass means the moon exerts a much weaker gravitational pull, with a surface gravity that is only about 13.4% that of Earth.
Europa’s lower overall density, approximately 3.013 grams per cubic centimeter, is explained by its composition, which includes a thick, outer layer of water ice and a subsurface ocean. Scientists estimate this ocean may contain two to three times the volume of liquid water found in all of Earth’s oceans combined, lying beneath an ice shell possibly 15 to 25 kilometers thick. This reduces the moon’s bulk density compared to Earth, which is dominated by a dense metallic core and rocky mantle.
Positional Context in the Solar System
Europa is not a terrestrial moon, but rather a satellite of the gas giant Jupiter, placing it in a completely different orbital environment. It orbits Jupiter at a distance of about 671,000 kilometers, completing one orbit approximately every 3.5 Earth days.
The distance between Earth and Europa constantly changes as both bodies orbit the Sun, but they are separated by a minimum of approximately 628 million kilometers (4.2 Astronomical Units). Light traveling from the Sun must first reach Europa, a journey that takes about 45 minutes. This separation emphasizes that Europa’s environment is defined by its proximity to Jupiter.