Majestic mountains of the Moon

The entire universe in blog form
June 30 2011 6:30 AM

Majestic mountains of the Moon

The Lunar Reconnaissance Orbiter takes amazing pictures of the Moon; I've posted dozens over the past couple of years. One of my favorite things is when the spacecraft snaps features I know: craters, mountains, winding valleys that I've seen myself behind the eyepiece. When I was younger I spent countless hours scouring the lunar surface with my telescope, and it's still a fun target when I haul my 'scope out to the end of the driveway.

And among the best of the best is the crater Tycho. You probably know it already; when the Moon is full the crater is bright, and the rays extending from it -- plumes of material ejected radially during the impact that formed the crater -- are extremely obvious. At 86 km (50 miles) across, it's a decent-sized hole in the surface, with a beautifully-defined system of central mountain peaks 15 km (8 miles) across. So when LRO sets its sights on Tycho's peaks, well... you get a gorgeous panorama like this:

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


You must click that to enlunenate it and see it in incredible detail. It's truly spectacular!

That peak rises about 2 km (1.2 miles) about the crater floor. Look how steep it is! I was mentally comparing it to the local foothills of the Rockies near where I live in Boulder, and realized it's not a bad analogy as far as size and shape go. In one way, hiking to the top of Tycho's peak would be easier, since the gravity is only 1/6th of Earth's... but while the air is thin here in Boulder, it's literally nonexistent on the Moon. So I'm thinking hiking Tycho would be somewhat more taxing.

But what a sight when you reached the top! Sitting smack dab on that largest peak is a boulder I'd very much like to see up close:

The view on the left is a closeup from the image above (here's a higher-res version), and the one on the right is from May 2010. The big difference is lighting and viewing angle; the left shot is lit obliquely and seen from the side, while on the right it's seen with a higher angle of sunlight and the view is nearly straight down.

That rock is huge, 120 meters across. An American football field would fit right on top of it, goalpost to goalpost. The smooth terrain around it is what's called impact melt, rock that was melted when the impactor hit over one hundred million years ago. That's why it looks smooth; it was probably molten material that flew off the surface and then rained back down.

But how did that rock get there? I have a hard time picturing something that big getting ripped off the surface by the impact and landing softly enough to stay intact. It looks out of place there, unlike the craggy peaks around it. I had thought perhaps it was fractured off one of those peaks and rolled to the local depression between them. I'm not so sure, and a web search didn't turn anything up on it. The top of the boulder appears to have some of the melt on it, too, so perhaps it really was blown out intact from the impact, fell back down after the peak formed, and then suffered through the rain of molten rock after.

I bet lunar geologists have lots of ideas about it... and I also bet we won't know for sure until one of them (or more likely, a colleague who is as yet in grade school right now) stands there with a pick and a bag, ready to take some samples back to the lab. Will her equipment be at Clavius base, I wonder?

Image credit: NASA/GSFC/Arizona State University

Related posts:


War Stories

The Right Target

Why Obama’s airstrikes against ISIS may be more effective than people expect.

The One National Holiday Republicans Hope You Forget

It’s Legal for Obama to Bomb Syria Because He Says It Is

I Stand With Emma Watson on Women’s Rights

Even though I know I’m going to get flak for it.

Should You Recline Your Seat? Two Economists Weigh In.


It Is Very, Very Stupid to Compare Hope Solo to Ray Rice

Or, why it is very, very stupid to compare Hope Solo to Ray Rice.

Building a Better Workplace

In Defense of HR

Startups and small businesses shouldn’t skip over a human resources department.

Why Is This Mother in Prison for Helping Her Daughter Get an Abortion?

Politico Wonders Why Gabby Giffords Is So “Ruthless” on Gun Control

Sept. 23 2014 4:45 PM An Up-Close Look at the U.S.–Mexico Border
  News & Politics
Sept. 23 2014 6:40 PM Coalition of the Presentable Don’t believe the official version. Meet America’s real allies in the fight against ISIS.
Sept. 23 2014 2:08 PM Home Depot’s Former Lead Security Engineer Had a Legacy of Sabotage
Sept. 23 2014 1:57 PM Would a Second Sarkozy Presidency End Marriage Equality in France?
  Double X
The XX Factor
Sept. 23 2014 2:32 PM Politico Asks: Why Is Gabby Giffords So “Ruthless” on Gun Control?
  Slate Plus
Political Gabfest
Sept. 23 2014 3:04 PM Chicago Gabfest How to get your tickets before anyone else.
Brow Beat
Sept. 23 2014 8:38 PM “No One in This World” Is One of Kutiman’s Best, Most Impressive Songs
Future Tense
Sept. 23 2014 5:36 PM This Climate Change Poem Moved World Leaders to Tears Today
  Health & Science
Sept. 23 2014 4:33 PM Who Deserves Those 4 Inches of Airplane Seat Space? An investigation into the economics of reclining.
Sports Nut
Sept. 23 2014 7:27 PM You’re Fired, Roger Goodell If the commissioner gets the ax, the NFL would still need a better justice system. What would that look like?