Mars Geology: Tooting Crater
One of the most interesting aspects of Martian geology that I have been involved with
recently is the analysis of a meteorite crater on Mars called "Tooting". Tooting is
the name of my home town in South London, England, and so I was delighted when I was
able to propose the name to the International Astronomical Union (IAU) and have the
name approved. (Note that there is quite an elaborate process that the IAU follows, so that
you just can't randomly propose any name and get it approved!).
You can see some of the general characterisitics of Tooting Crater in the image below.
Mars has some very unusual impact craters compared to examples on the Moon or Mercury because
many Martian craters have a distal ridge (or "rampart") around the perimeter of the ejecta
blanket. This is believed to have formed from a ground-hugging flow created as the impact
took place in a volatile-rich target. Tooting Crater is a very fresh example of a rampart
crater, because it shows minimal signs of erosions and there are almost no small impact craters on the ejecta blanket.
Tooting Crater is about 28 km in diameter, and is located at 23.4N, 207.5E, just to the west of Olympus Mons
volcano (which is often cited as the largest volcano on Mars). It is very hard to get an absolute age for the crater, but based upon the number of smaller craters which have formed since Tooting Crater, a good guess at the how long ago Tooting Crater was formed would be 3 to 5 million years ago. You can see the location of Tooting
in the map below, which is a MOLA elevation map of Mars. We can use the same cratering counting technique to estimate that the rocks within which Tooting formed might be about 1.3 billion years old. As Tooting Crater is a very young crater that formed on relatively
young (for Mars) lava flows, Tooting may represent a potential source for some of the Martian meteorites (which
also have a young age and are volcanic rocks).
I have published a number of papers on the geology of Tooting Crater. See the following for detailed descriptions of the geology of the crater and how we are using these investigations to learn more about the older, more eroded, craters on Mars:
Mouginis-Mark, P.J. and H. Garbeil (2007). Crater geometry and ejecta thickness of the Martian impact crater Tooting. Meteoritics and Planetary Science, 42, 1615 - 1626.
Morris, A. R., P. Mouginis-Mark and H. Garbeil (2010). Possible impact melt and debris flows at Tooting Crater, Mars. Icarus, 209, 369 - 389.
Mouginis-Mark, P. J. and J. M. Boyce (2012). Tooting crater: Geology and geomorphology of the archetype large, fresh, impact crater on Mars. Chemie der Erde Geochemistry, 72, p. 1 - 23.
I have also created a 1:200,000 scale geologic map of the crater, and this map will be published in mid-2015 by the U.S. Geological Survey as Scientific Investigations Map 3297. A small version of this map is shown below.
Topographic data from the MOLA instrument allows a profile across the crater to be derived.
You can see that the crater has a rim that is about 700 meters high, and that the floor of the
crater is about 1,200 meters below the level of the pre-existing terrain. There is also a
prominent central peak in the interior of the crater that rises about 500 meters above the
level of the crater floor.
Tooting Crater is also unusual as Martian meteorite craters go because there is a large number
of smaller craters (called "secondary craters") around the perimeter of the ejecta blanket. The image
below shows some of these secondary craters, which are believed to have formed when blocks of
material thrown out of the crater cavity during the impact event re-impacted the surface. There
is just a chance that one such block, instead of landing back on Mars, escaped the gravity of Mars
and travelled to earth, to be found here as one of the Martian meteorites. If this is the case,
then the age of the meteorite (~1.3 billion years old) is also the age of the lava flows within
which Tooting Crater formed.
Tooting on Earth!
My old home town isn't quite as scenic as eastern Amazonis Planitia on Mars, but it still has a lot going for it.
One thing is its long history!
Tooting was first described back in the year 675 A.D., when it was called "Totinge". It was also mentioned in the
Domesday Book in 1086. At that time, it comprised two manors - namely Upper Tooting and Tooting Bec.
It was owned by the Abbey of St. Mary of Bec in Normandy, France, which is where the name "Tooting Bec" comes from.
"Tooting" comes from the name of the Saxon Tota and follows the old English custom of adding "ing"
(which means "the people who lived at") to the person's name. Thus "Tooting" literally means "The home of Tota's people".
And here, for your viewing pleasure, are a few views of Tooting, London (circa July 2006):
The naming of Tooting Crater on Mars has, amazingly, attracted some media attention back in England, which has prompted
some of my old friends in the UK to have a new interest in Martian geology! Most of the coverage has now been removed from the Internet as it is "old news".
But if you want to see some of the coverage, take a look at:
And if you want to know more about the "real" Tooting, check out the following links: