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Somewhere Over the Bay of Rainbows

Posted By Bill Dunford

02-12-2013 12:35 CST

Topics: pretty pictures, Lunar Reconnaissance Orbiter, the Moon, Chang'E program

China's first lunar lander, which also happens to be humankind's first in nearly four decades, is on its way to the Moon. The Chang’e 3 spacecraft departed Earth on December 2 local China time, carrying the Yutu (Jade Rabbit) rover.

Chang’e 3 is headed for a mid-December landing on a broad plain called Sinus Iridum, "The Bay of Rainbows." Sinus Iridum is found at the northwest edge of Mare Imbrium, or "Sea of Rains." It's an impact basin a couple of hundred kilometers wide that was filled in by floods of basaltic lava. At its "shores" is a semi-circular ring of dramatic mountains called Montes Jura, with the Heraclides Promontory at its western tip and the Laplace Promontory at the eastern tip.

Sinus Iridum

NASA / ASU / Bill Dunford

Sinus Iridum
A terrain model of the Moon's Sinus Iridum, the Bay of Rainbows, a 236-km wide impact basin filled with basaltic lava.

This area is over 1,000 kilometers from the nearest Apollo landing site, and it could provide lunar explorers with a rich set of information about the Moon and its history.

Thanks to NASA's Lunar Reconnaissance Orbiter, we can make an advance visit of our own. Following are a few extreme close-ups of the Bay of Rainbows, courtesy of LRO's sharp-eyed cameras, which can make out objects as small as the equipment left of the surface by the Apollo astronauts, and even their foot trails.

One of the first things that becomes apparent when looking through LRO's Sinus Iridum data is that this plain, which looks so smooth from a distance, is a little more...complicated than you might think. I purposely chose the most featureless section of the bay that I could see, and found that images from this area typically look like the following.

Rough Features of a Smooth Plain


Rough Features of a Smooth Plain
Sinus Iridum, "The Bay of Rainbows," is one of the smoothest areas of the Moon, and parts of it appear almost featureless from a distance. But when the Lunar Reconnaissance Orbiter trains its high-resolution camera on even the flattest sections of the plain, it reveals a complex surface of craters, ejecta, and boulders.

There will be no shortage of rocks and craters for Yutu to explore.

Here's one interesting crater among many, an apparently (relatively) young example with bright ejecta and what looks like rings of melted rock.

Bright Unnamed Crater in Sinus Iridum


Bright Unnamed Crater in Sinus Iridum
A relatively recent impact has exposed light material from beneath the surface of Sinus Iridum on the Moon, as seen in detail by the Lunar Reconnaissance Orbiter.

If the Jade Rabbit wandered far enough to reach the edge of the bay, it would be able to explore Promontorium Laplace, a cape marked by mountains that rise as much as 2600 meters above the lava plains. It was named for Pierre Simon marquis de Laplace, who was a French astronomer in the 18th century.

Here's a close look at the exact point where the plains meet the Laplace headlands and its intriguing geology.

Edge of the Bay


Edge of the Bay
The eastern edge of the Moon's Sinus Iridum plain where it meets the mountains of Promontorium Laplace. The promontory reaches about 2600 meters above the plains at its highest point. The boulders at the foot of the wall in this image are a few tens of meters across. Imaged by the Lunar Reconnaissance Orbiter.

Imagine the view from on top of the hill!

If the Chang'e 3 landing goes well, we won't have to imagine the view from the plains, as we follow along with Yutu's adventures on the surface of the Moon.

See other posts from December 2013


Read more blog entries about: pretty pictures, Lunar Reconnaissance Orbiter, the Moon, Chang'E program


Bob Ware: 12/02/2013 06:46 CST

Those ground views are going to be awesome.

Rob: 12/03/2013 09:38 CST

Awesome photos and a nice article. So as smooth as it looks it's really rough as a cob up close. Isn't this where Arthur Clarke's novel "A Fall of Moondust" took place?

Bill Dunford: 12/03/2013 12:03 CST

Bob, bet you're right. Rob, thanks. That novel is actually set in Sinus Roris, the "Bay of Dews".

Bob Ware: 12/05/2013 10:41 CST

A week from Sat. is the best guess for a landing... 12/14/2013. The target has not been officially released...just the general area. Of course we did that a Mars with Viking... had to wait for the storm to subside to see where we could land. In this case I think they are going to wait to see what the mechanics play out to since this is their 1st landing attempt. I hope they have a great landing and mission.

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