"It is almost like flying above a haze layer and looking down through the haze at the surface. Ejecta from that crater (Proclus) does not look like it is resting on top of Crisium. It looks like it is suspended over it."

- Apollo 15 command module pilot Alfred M. Worden, (El Baz, Worden et al., The Proceedings of the 3rd Lunar Science Conference, 1972, p. 95)

"It looks artificial. It's almost incredible that such a thing could have been formed in the first instance, or if it was formed, could have lasted during the ages in which the moon has been in existence."

- Comment about an alleged 12-mile long bridge-like structure in Mare Crisium made by British astronomer Dr. H. P. Wilkins in a BBC radio interrview (Patrick Moore's Armchair Astronomoy, Patrick Moore, 1984, Patrick Stephens Ltd., U.K.)

Mouse-Sensitive Map - Mare Crisium: LO4-191H3 (green areas are mouse sensitive).

(Or click here  for the Picard page and here  for Peirce.


The Hunt Begins

Astronaut Worden's intriguing statement is not elaborated upon in the Conference proceedings. Selenologist Farouk El Baz says only that it was a "vivid" description of the appearance of Mare Crisium. We have not yet verified the source of the comment allegedly made by Dr. Wilkins; the reference to Moore's book was found in another source so we only have this second-hand. And we have found no mention yet of this "bridge" in any astronomy and selenology literature. But these two quotes were sufficient to send us intrepid lunar anomaly hunters off in pursuit of Apollo and Orbiter photographs of Mare Crisium.

I acquired several Apollo photographs and one Lunar Orbiter 4 photograph  (191H3) of Mare Crisium in the summer of 1995. After a cursory examination of the photographs, I concluded that there was no evidence of any fantastic 12-mile long bridge over Mare Crisium, and that the rays from the crater Proclus looked firmly attached to the top soil as far as I could tell.

Disappointed, I put all my Mare Cris photographs away and did not look at them again until a few months ago when I noticed Jon Floyd's description on his Clementine web page of one photograph of the crater Picard  in Mare Crisium. Jon said that the hazy appearance of that crater suggested that there might be a dome over it. I informed him that he had to be mistaken, because my Apollo photographs, which are much higher-resolution than Clementine's, showed no such thing. To prove my point, I sent a gif from Apollo 10, Frame 4421 of Picard out to other VGL members (someday we'll tell you what "VGL" stands for, but not now). Bill Kohler sent the gif back to me, marked up with lines to indicate what he said looked to him like arches over Picard - the possible remnants of a dome. These "arches" are more subtle than what I had originally been looking for, but they are no less intriguing, and so we began looking at the other photographs of the Mare Crisium region more closely than I had initially, and we have been going over the images for several months. Mike Lomax and Jon Floyd also sent back marked-up gifs highlighting their observations of unusual-looking features in Picard and on the surrounding mare surface.

My attempt to "debunk" the dome over Picard seems to have back-fired rather badly, and now I've got to do all this work on these Crisium web pages. Oh, well.

Mare Crisium Description

Mare Crisium is a relatively young mare region, but older than the two most recently-formed maria, Imbrium and Orientale. It is 350 miles in diameter in the east-to-west direction and 270 miles in the north-to-south direction and covers an area of 66,000 square miles. Centered at approximately 20 degrees north and 60 degrees east, it is near the eastern edge of the side of the moon visible from Earth. It is one of the more striking features of the lunar surface as viewed from Earth. Mare Crisium is the site of a gravitational anomaly known as a "mascon," or mass concentration. The mascon is presumably the fragments of the asteroid or comet whose impact created the mare basin buried beneath the surface. The high-gravity anomaly associated with the mascon makes the already-complex task of computing the orbits of lunar space probes all the more difficult. It also causes lunar satellites orbiting at low altitudes to either impact the moon or to be flung out into interplanetary space after a few years.

Picard and Peirce Craters

Picard has been the primary focus of our attention in recent months, and a more detailed description of what we think we have found in Picard together with the images is here. Another crater named Peirce also proved to be unusual on closer inspection of Lunar Orbiter 4, Frame 191H3. Peirce is to the north of Picard. Both are "Class 1" craters, which means that they are both relatively "young," formed after the basalts had been laid down in the mare basin. The young age of these craters is an especially important factor in our evaluation of Peirce, as will be explained on the Peirce web page here.

These two craters also seem to have been the source of a "puzzling" concentration of magnesium-bearing minerals and glasses found in the regolith in Mare Crisium by Luna 24, a Soviet probe that landed in the mare far to the south of Picard.The concentration of magnesium in the regolith sampled by Luna 24 was significantly higher than the concentrations found in the core drillings made by the probe into the underlying basalt ("Evidence for a high-magnesium subsurface basalt in Mare Crisium from orbital X-ray fluorescence data," Constance G. Andre, et al., Mare Crisium: The View from Luna 24, Pergamon Press, (New Your), p 1-12).The X-ray measurements made by the Apollo 15 XRF experiment from orbit indicated that high concentrations of titanium oxides and magnesium oxides and low concentrations of aluminum oxides were centered on both Picard and Peirce. The inference made by selenologists is that the impacts that formed Peirce and Picard excavated a high-magnesium substratum of basalt beneath the magnesium-poor basalts in the core sample made by Luna 24. We, of course, have some different ideas about the possible source of these high concentrations of magnesium and titanium. We'll be talking about this more, especially in reference to Peirce.

In keeping with the VGL philosophy of never finishing anything we start, this Crisium page will be permanently under construction. We will be adding to it at irregular intervals, so if you find this subject interesting or at least entertainingly eccentric, please check back every few weeks or so. You never know what you might find here.

Lan Fleming

Note on Support Data Access In the past, I have put the support data on the same page with the images and their descriptions and interpretations. For Mare Crisium, however, we are preparing a large number of images from each of several photographic negatives. In order to make this support data easily available to those who are interested in the details without cluttering up the pages discussing the images, there is one support data page on Crisium for all photographs and digital images. Anchorswill be established from the discussion pages to the appropriate support data. The support data is organized with the information on the preparation of the digital images listed under the NASA support data for the photograph from which they are derived.