The Red Planet Makes Closest Approach in 11 Years With Mars at Opposition
A few days before Mars was directly in opposition to Earth (the point where Earth is directly between the sun and Mars), the Hubble Space Telescope snapped a portrait.
It was great timing. Not only is Mars at opposition, which means the sun provides a fully illuminated view of the planet, it is also as close as it has been to Earth in the last nine years -- at only about 50 million miles.
The shot, which shows details as small as 20 to 30 miles across, shows a receding northern polar cap (it is now late summer in the northern hemisphere), a cloud-covered southern polar cap, and a vivid, rust-colored landscape.
The orange area in the center of the image is Arabia Terra, a vast upland region in northern Mars that covers about 2,800 miles. The landscape is densely cratered and heavily eroded, indicating that it could be among the oldest terrains on the planet. Dried river canyons (too small to be seen here) wind through the region and empty into the large northern lowlands.
The large, dark region to the right of Arabia Terra is Syrtis Major, an ancient, inactive shield volcano that was one of the first features identified on the surface of the planet by seventeenth century observers. In fact, Christiaan Huygens used this feature to measure the rotation rate of Mars. (A Martian day is about 24 hours and 37 minutes.)
A large oval feature to the south of Syrtis Major is the bright Hellas Planitia basin. About 1,100 miles across and nearly five miles deep, it was formed about 3.5 billion years ago by an asteroid impact.
South of Arabia Terra, running east to west along the equator, are the long dark features known as Sinus Sabaeus (to the east) and Sinus Meridiani (to the west). These darker regions are covered by dark bedrock and fine-grained sand deposits ground down from ancient lava flows and other volcanic features. These sand grains are coarser and less reflective than the fine dust that gives the brighter regions of Mars their ruddy appearance.
To the west of Arabia Terra is Acidalia Planitia, a massive, flat plain that may have been covered by an ancient ocean. Well know to fans of the movie "The Martian", Acidalia Planitia sits just north and slightly east of Valles Marineris, whose eastern edges can just be seen on the left.
This portrait of Mars was made just a few days before Mars at opposition -- when the sun and Mars are in a line and directly opposite each other as seen from Earth -- and when Mars will be at a distance of 47.4 million miles from Earth.
With Mars at opposition, the planet is fully illuminated by the sun as viewed from Earth, making it a particularly good time for viewing.
On May 30, Mars will be the closest it has been to Earth in 11 years, at a distance of 46.8 million miles.