Earth Moon Comparison
May 09, 2001
The above image shows the Earth and the moon as viewed from the Odyssey spacecraft on its journey to Mars. Even though the Earth and its satellite look pretty small (the moon is a mere speck), at the time this photograph was taken (late April), Odyssey was more than 15 times closer to the Earth than to Mars - it was 4,639,830 km (2,883,050 miles) from Earth. The spacecraft won't arrive at Mars until October 24 - it was launched on April 7. Odyssey carries three scientific instruments designed to tell us what the Martian surface is made of and its radiation environment.
This image shows the true distance relationship between the Earth and the moon as well as the size difference comparison. Earth and its satellite are approximately 385,000 km apart - about 30 Earth diameters. Odyssey is traveling at a speed of 3.3 kilometers per second (7,474 miles per hour) relative to the Earth. Even though the Earth has a diameter of 12,756 km compared to a diameter of 3,476 for that of the moon, since this image was taken in infrared light, the moon looks smaller than it's actual size. It's much cooler (less emissive), and thus it's not as bright as is the Earth. The darker area on the lower portion of the Earth's disk is Antarctica.