General Moon Resources

A New Way to Find Oceans on Other Worlds Revealed by the Moon

April 7th 2009

Sally Langford, a doctoral candidate in physics at the University of Melbourne  used a backyard telescope to make a potentially big discovery: Earth’s oceans and continents shine differently on the dark side of the moon.

She is suggesting the “earthshine” of planets around other stars could provide long-distance “view” into their surface features.

Langford and her colleagues, from Melbourne and Princeton University, have shown that earthshine from the moon varies with the Earth’s land masses and oceans. As the earth turns, the reflection colour and intensity changes and can be seen on the dark side of the moon. Their paper appears in the international journal Astrobiology.

This is the world’s first study to use the reflection of the Earth to measure the effect of continents and oceans on the apparent brightness of a planet. Other studies have used a color spectrum and infrared sensors to identify vegetation, or for climate monitoring.

The researchers watched the dark side of the crescent moon using a 20 cm (8 inch) telescope. this is considered to be on the bigger side of what most amateur astronomers use in their yards.

Langford took images of the Moon for about three years to measure the earth’s brightness as the earth rotated. Observations of the Moon were made from Mount Macedon in Victoria for three days each month when the Moon was rising or setting. The study was conducted so that in the evening, when the Moon was a waxing crescent, the reflected earthshine originated from Indian Ocean and Africa’s east coast. In the morning, when the Moon was a waning crescent, it originated only from the Pacific Ocean. her Paper can be read below:

http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2008.0267

Langford’s setup for observing the Moon. Credit: Stuart Wyithe, second author, a physicist at the University of Melbourne.