Summary: A few of the reports that have been investigated by GEPAN/SEPRA show ground traces that may be associated with the events reported by witnesses. Similar cases have been documented by other investigators. Phillips (1975) prepared a catalog of 561 such cases as a CUFOS report.
A few of the reports that have been investigated by GEPAN/SEPRA show ground traces that may be associated with the events reported by witnesses. Similar cases have been documented by other investigators. Phillips (1975) prepared a catalog of 561 such cases as a CUFOS report.
GEPAN/SEPRA has investigated only cases for which the following conditions are met:
Information concerning the event has come to GEPAN/SEPRA from an official source such as the Gendarmerie, local police, etc.
The event is recent (a few hours to a few days old).
The area has been protected and the traces have been preserved.
Sampling and measurements have taken place within a short time after the event.
Meteorological conditions have been favorable for preservation of the traces (no rain, etc.).
It is also desirable, but not essential that the event has independent credible multiple witnesses.
The first steps — to protect the site, to make measurements, and to begin collecting samples — are usually carried out by the Gendarmerie who have a complete set of instructions in a manual prepared by GEPAN/SEPRA, who have also devised procedures to be implemented by specialized laboratories for the collection and analysis of samples. When the services of a specialized laboratory are requested, the laboratory personnel will go to the site for in situ sampling.
Soil has the capability of retaining the effects of several processes including mechanical, thermal, magnetic, radioactive, and physicochemical processes.
Mechanical: A continuous or brief mechanical pressure causes a distortion of the soil. The compression of the soil can be measured by a penetration instrument, for instance.
Thermal: Measurement of the quantity of water in the soil, as compared to nearby control samples, allows determination of the amount of energy required to reduce the water content to that level.
Magnetic: Some soils have a high magnetic remanence. In this case, it is useful to examine the magnetic pattern of the soil with the help of magnetometers either in situ or (after sampling) in a laboratory.
Radioactivity: Such measurements may be made in situ or carried out on samples in the laboratory.
Physicochemical: Samples from the trace region and control samples away from the trace region can be analyzed for molecular, atomic and isotopic composition, etc.
Velasco described in detail their investigation of an event that occurred near Trans-en-Provence, France, on January 8, 1981 at about 5:00 p.m. (Bounias, 1990; Vallee, 1990; Velasco, 1990; see Section 15.) One weakness of this case is that there was only one witness. The witness was working in his garden when he heard a low whistling sound. Upon turning around, he saw an ovoid object in the sky that approached the terrace at the bottom of the garden and landed. The witness moved forward cautiously to observe the strange phenomenon but, within a minute, the object rose and moved away in the same direction from which it had arrived. It continued to emit a low whistle. The witness approached the scene of the apparent landing and observed circular depressions, separated by a crown, on the ground.
The Draguignan Gendarmerie arrived the next day (January 9) to investigate the report and, following GEPAN/SEPRA instructions, took samples from the ground and from the vegetation. The Gendarmerie found two concentric circles, one 2.2 meters in diameter the second 2.4 meters in diameter. Between the two circles was a raised area 10 cm wide. They found, on this raised area, two sectors, diametrically opposite, each about 80 cm long, that contained black striations similar to abrasion traces.
A team from GEPAN/SEPRA carried out a site visit on February 17, 1981, 40 days after the event. The trace was still visible since there had been very little rainfall since January 8. The arc-shaped area, lighter than the rest of the terrain, was still visible. The soil in this region was heavily compacted, forming a crust. Soil samples were taken both on January 9 and on February 17. These samples were then forwarded to various laboratories equipped for physical and chemical analyses. It was found that the compacted soil had a thickness of 6-7 mm. There was no trace of organic compounds such as one might expect to be produced by combustion. There was some evidence of iron in the form of striations about 1 micron thick, but the iron was not accompanied by chromium, manganese or nickel as would be the case for steel. There was some evidence of polymers. Traces of phosphate and zinc were also found. Traces visible as striations seemed to have been produced by a combination of mechanical and thermal effects.
Visual and microscopic examination revealed that, apart from the striations, the soil had been compacted without major heating, since the structure of calcium carbonate was not affected. Velasco has made an order-of-magnitude estimate indicating that, to produce the measured compression of the soil, one would need a stationary object of about 700 kilograms. On the other hand, the same indentations in the soil could have been made by an object of lower mass if the object were moving at a few meters per second at the time of impact.
The panel was intrigued to learn that ground traces appear to be associated with some UFO reports. These traces could of course be spurious with no relation whatever to the reported event, they could be due to hoaxes, or they could in fact be related to a real event. Clearly, it is essential to devise measurement procedures that can distinguish between these three possibilities. For this to be possible, it would definitely be helpful to have "baseline" measurements for some likely spurious causes and for hoaxes. The possible spurious causes would of course depend upon the location in which the event occurs. For instance, in the Trans-en-Provence case in which the event occurred in a vegetable garden, the trace may have been caused by some piece of gardening equipment such as a metal water barrel. Similarly, someone perpetrating a hoax might have used a standard or manufactured wheeled object. Rather than leave the effects of such spurious causes or hoaxes up to speculation, it would clearly be advantageous to have firm information on which to base a judgment such as could be provided by relevant experiments. The investigators could move a water container to a similar patch of earth, or create a trace with a wheeled heavily laden object, and then compare measurements of those traces with measurements of the trace associated with the UFO report.
Experiments such as the above could be specific to a particular case or they could be generic. If such experiments became the rule rather than the exception, it would become possible for an investigator to consult a catalog of spurious causes or of hoaxes as well as a catalog of claimed "real" events.
For further information about the Trans-en-Provence case, see Section 15.