The Earth and Moon shot from 142 million kilometers: two dots in space

The impressive image, showcasing the Earth and the Moon was captured at 5:20 a.m. MST on Oct. 3, 2007, from a staggering distance of 142 million kilometers by NASA’s Mars Reconnaissance Orbiter probe, which was circling the Red Planet, Mars. The HiRISE instrument was instrumental in this process, with a scale of 142 km/pixel and the Earth and Moon exhibiting diameters of about 90 pixels and 24 pixels, respectively. At a phase angle of 98 degrees, less than half of the Earth and Moon’s disks are directly illuminated. One can expect maximum disk illumination when Earth/Moon are on the opposite side of the Sun from Mars. However, this increased distance would compromise the image’s detail.

Diving Into the Image Details

In the Earth’s image, the west coast of South America can be discerned in the lower right corner, albeit cloud formations are the most prominent feature. These clouds shine so brightly against the Moon that they appear saturated in the HiRISE images, which were produced using three filters – red, green and blue, culminating in a composite image. The red filter image was largely saturated, the blue-green image exhibited significant saturation, and the brightest clouds appeared saturated in the IR image. To produce a visually appealing version, substantial processing was required. The Moon’s image, while unsaturated, is intensified relative to Earth, making it valuable for camera calibration.

Earth and Moon: A View from 142 Million Kilometers. Credit: NASA/JPL-Caltech/UArizona