# June 1991

### The return of the Martian canal-builders

The human brain has an astonishing ability to find familiar patterns embedded in chaotic backgrounds. After all, clouds sometimes take on the appearance of faces. Gardner relates that the Canadian one-dollar bill had to be re-engraved because the face of a demon accidentally turned up in the Queen's hair just behind her left ear. The surface of Mars gives us two more examples: Mars has an impact crater that seems to have a "smiling mouth" and "eyes," apparently fractures caused on impact. This five-mile-wide feature has been dubbed the "Happy Face."5 Elsewhere on the Martian surface is a lava flow with a small impact crater that looks like Kermit the Frog.6 Neither of these are of artificial origin. Why then should one assume that the Mars "face" is more than just a rock formation? We should not make such an assumption unless there is strong evidence that the "face" is not an isolated feature.

### Unsuspected dangers of extrapolating from truncated analyses

Differential calculus is central to the physical sciences. Analyses of phenomena described by Maxwell's equations, Navier's equation, the Navier-Stokes equations, or the Korteweg-deVries equation, etc., all need differential calculus. Limits are essential to differential calculus. Differentiation of a function f(x) about a point x0 as a casual perusal of calculus textbooks as well as Newton's notebooks will suffice to show,3 has a geometric interpretation in which the spread (xb - xa) of the range xa ≤ x0 ≤ xb is made increasingly small until it almost vanishes. Assuming that f(x) is continuous, this limiting process yields its derivative at x0. Or, does it?

### The Face on Mars: Summary of Image processing results

The "Face on Mars" has been the subject of a small and unusual debate for over 10 years. Initially dismissed by NASA as a trick of light and shadow when it was imaged by a Viking Orbiter in 1976, the "face" was rediscovered by DiPietro and Molenaar several years later. A series of independent investigations followed, which have prompted curious reactions from the planetary science community. The accompanying article by Crowe states a view expressed by many in that community that the "face," along with several other nearby objects, are naturally occurring geological formations.

### Progress in Capacity, Cost/Byte Critical for Optical Data Storage

If optical data storage is to make further inroads in meeting the digital data storage needs that may also be satisfied by ongoing improvements in magnetic recording, continued performance enhancement and reduced cost/byte stored is essential. That was the message that keynote speaker Vic Jipson of IBM Almaden Research Center brought to the 1991 Topical Meeting on Optical Data Storage held in Colorado Springs, February 25-27.

### International standards ready for review

There is so much new work going on in the international standards arena that this month we will simply list some of the draft standards now out for review and comments. A brief abstract of each document is included to give a feel for the scope of the standard. As you look over the list, it is obvious some of these standards will have a significant impact on individuals and industries using the optical equipment covered.

### Fancy footworks Understanding funhouse mirrors

The Reuben H. Fleet Space Theater and Science Museum has a number of displays for interactive use by children. One of the most puzzling (to children and adults alike) is the so-called "footwork" mirror. This small display on the second floor consists solely of a mirror curved around horizontal axes into a shallow "S" shape. It is placed at the wall so that, upon passing, one sees a short stubby leg hanging isolated in space with a foot on the top facing upward and another on the bottom more or less normally situated.

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