Mars-eye view delivers new perspective on the Earth and Moon
One of the strengths of photography is the ability for images to provide a new perspective on something familiar. If images of the Earth from the Moon have become a little ho-hum, how about an image of the Earth and the Moon from Mars? Courtesy of the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO), we have a new view of our home planet and its nearest neighbor.
Taken at a distance of around 127 million miles (205 million km) from Earth, the images were taken to calibrate data collected by HiRISE using the reflectance of the Moon's Earth-facing side, which is well known. So that the Earth doesn't appear too bright or the Moon too dull, the composite image brings together the best Earth image and best Moon image from four sets of images snapped on November 20, last year.
In the image, the Moon appears much closer to the Earth than the roughly 30 times the diameter of the Earth it actually is. This is because the images were collected when the Moon was almost directly behind the Earth so as to capture the Earth-facing side of the Moon. However, the sizes and positions of the Earth and the Moon are correct relative to each other in the composite image.
Despite the distances involved, the images have a high enough resolution to make out continents on Earth. The bright white at the bottom of the Earth is Antarctica, while Australia can be made out as the large reddish feature in the middle.
This isn't the first image of Earth and the Moon snapped by the HiRISE camera. In October, 2007, it captured the above image from a distance of 88 million miles (142 million km). But due to the phase angle of 98 degrees, less than half the disks of the Earth and the Moon are directly illuminated.
The only time it would be possible to capture images of the Earth and Moon at full illumination is when the Earth and Mars are on opposite sides of the Sun, which would result in much less detail due to the much greater distances involved.