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Where on the Moon is Jack Schmitt's Hammer?

Copyright © 1999 by James V. Scotti.
All rights reserved.
Last revised 09 August 2001.


One of the last things that Harrison H. "Jack" Schmitt did while on the surface of the moon at the end of the last lunar EVA of the Apollo program was to throw their one and only Geology hammer off into the distance. Where did the only Geology Hammer ever to be carried on the moon by a professional Geologist actually end up?

The answer lies in four photographs taken by Gene Cernan to document the hammer throw and from others taken from the LM cabin after the EVA.

First, look at AS17-143-21938 to see Gene Cernan's first image after the hammer throw (sorry, there are no images of Schmitt actually in mid throw, except for the distant video record taken by the TV camera on the rover). Frame 21938 is a slightly blurred black and white image. Not only can you see the western flank of the North Massif to the right and in the distance, (Old) Family Mountain (center) and the hills bounding the western exit from the Taurus-Littrow Valley out into Mare Serenitatis out beyond, but also, you can see the ALSEP central station and a number of boulders nearby left of center as well as a myriad of rover tracks and astronaut boot tracks. Also visible, in the dark black sky is a small white line - the hammer in mid-flight. Zooming in, we can see a slightly blurred hammer with the head on the left.

Gene's second picture, AS17-143-21939 contains a similar view, but with the hammer nearly end on.

The third image, AS17-143-21940, shows the impact of the hammer on the lunar surface. Just right of the center of the image, to the right of the ALSEP Central station (between and just above the second and third reseau marks (crosses) from the righthand edge in the second row up from the bottom of the image) you can see a small dark vertical arc and a black horizontal line (horizontal at least compared to the Lunar horizon as the image is tilted) to its right which is the lunar dust flying away from the impact site. Zooming in, you can see the plume in more detail. The raw image is in the center, a version enhanced to emphasize the portion of the plume seen against the black lunar sky is on the left, and a version enhanced to emphasize the portion with the lunar surface as a background is on the right.

The final image in the sequence is AS17-143-21941 , which shows Jack Schmitt, possibly as he watches the dust spray settle.

Image AS17-143-21944 was taken after the 3rd EVA towards the ALSEP site from inside the cabin. After viewing the closeup, return to this image and look closely, just above and left (at about 10 O'Clock) of the right crosshair, in the dark patch of disturbed soil. You can see the hammer just barely in this image. Looking closely to the right and below the ALSEP central station (which appears at the top left of this blown up portion of the previous frame), near the lower right corner of this image is a small straight, but slightly irregular feature - the hammer, lying out on the lunar surface. There are other images of the hammer taken out the window after EVA-3, but frame 21944 is the best of them.

Jim Scotti, August 29, 1999.

P.S. In an October 2000 note, Jim adds "I recently piled two post-EVA images of the ALSEP site together, one taken from the CDR window and one from the LMP window, to get a stereo view. It's great to see that little ridge pop out so obviously. I remember watching the video of Schmitt carrying the ALSEP pallet out to the ALSEP site and watching him disappear over that ridge. Unfortunately, the overlap doesn't include the hammer's location, it's just out of view of the CDR side image."

And, in an August 9, 2001 note, Jim writes, "I finally sat down to figure out how far away Jack Schmitt's hammer is from the LM. Here's the summary. You mentioned that the hammer was 39cm long. The Reseau fiducials have been measured to be about 10.3 degrees apart assumming a 53.5 degree image width and 2.59 fiducial separations from center to edge of frame. I estimated the hammer to be 0.050 fiducial seps long and only 0.008 fiducial seps tall. Ignoring the foreshortening, it is 0.51 degrees long which translates to 44 meters away from the LM. As a check, I estimated the LRV wheelbase at the estimated distance of the hammer to be about 2.1 meters. I also estimated the height of the ALSEP central station given that it is 190 meters away as 1.1 meters tall. I haven't been able to find the LRV wheelbase or the central station height anywhere yet, but based on pictures of the central station and the LRV, those are definitely pretty close to the right answers, certainly well within the measurement errors and approximations (lack of detailed accounting of the foreshortening, mainly)."

Figure 1-1 in the LRV Handbook gives a wheel base of 72 inches or 1.83 meters. This suggests that the hammer is a bit closer to the LM than 44 meters. If the hammer isn't lying perpendicular to the line of sight, it's apparent length would be a bit less than 39 cm (foreshortening), and the estimated distance would also be somewhat less than 44 meters.


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