4.1. Observations of iron-rich and silicate spherules

Iron-rich spherules were also observed in studies conducted by the RJ Lee company [1] and the US Geological Survey (USGS) [2]. In particular, a USGS report on the WTC dust provides two micrographs of “iron-rich spheres” [3] and a “bulbous” or tear-drop-shaped silicate droplet [4] (see images below).

No explanation for the presence of these iron-rich and silicate spheres (which imply very high temperatures along with droplet formation) is given in the published USGS reports.

The RJ Lee report also provides a micrograph and XEDS data for iron-rich spheres observed in the WTC dust; for example, their figure 21 (below, left) shows an “SEM image and EDS of spherical iron particle [1].” We likewise observe high-iron, relatively low oxygen spheres (e.g., below right and Fig. 4), which we find are unlike spheres gathered from cutting structural steel with an oxyacetylene torch.

Moreover, the RJ Lee report provides provocative data regarding the abundance of observed iron-rich spheres. A WTC dust sample acquired at 130 Liberty Street shows a “mean of composition” of “Fe spheres” of 5.87% which is very high compared with “Fe spheres” found in ordinary building dust of only 0.04% [1]. As the report notes, the WTC dust has unusual identifying characteristics – in particular, the WTC

dust in this sample has nearly 150 times (5.87/0.04) the amount of iron-rich spheres as ordinary dust

(where Fe spheres can arise from micrometeorites, for example).

There are other identifying features that characterize WTC dust compared with ordinary office dust; the RJ Lee report concludes:

“Various metals (most notably iron and lead) were melted during the WTC Event, producing spherical metallic particles. Exposure of phases to high heat results in the formation of spherical particles due to surface tension…”

“In addition to the vesicular carbon components, the high heat exposure of the WTC Dust has also created other morphologically specific varieties of particulate matter including spherical metallic, vesicular siliceous and spherical fly ash components. These types of particles are classic examples of high temperature or combustion by-products and are generally absent in typical office dust…”

“Particles of materials that had been modified by exposure to high temperature, such as spherical particles of iron and silicates, are common in WTC Dust because of the fire that accompanied the WTC Event, but are not common in “normal” interior office dust…”

“Combustion-related products are significant WTC Dust Markers, particularly if seen in combination [5].”

We agree with the RJ Lee report that the abundance of “spherical particles of iron and silicates” is proof of high temperatures, and that these particles are not common in normal office dust, but we do not agree that this abundance is necessarily due to the “fire that accompanied the WTC Event”. Before drawing such a conclusion, one must scrutinize the temperatures and other conditions needed to form these molten spheres (iron melts at 1,538 °C (2,800 °F) while iron (III) oxide melts at 1,565 °C (2,849 °F) [6] and aluminosilicates melt around 1,450 C [7]) and then compare with conditions reached in the WTC fires. We will turn to this task, after considering other data which also point to anomalously high temperatures during the WTC destruction.

4.2. Volatilized lead

The RJ Lee report notes “extremely high temperatures during the collapse which caused metallic lead to volatilize, oxidize, and finally condense on the surface of the mineral wool [1].” Again, “metals were vaporized at the WTC during the WTC Event and either deposited on WTC Dust or deposited directly onto surfaces in the Building [1].” Where do the requisite high temperatures come from?

An additional characteristic of WTC Dust is the presence of coated particles and fibers. The coatings vary in thickness from monolayers to finely-dispersed sub-micron sized particles. The coated particles have been detected by low voltage back-scattered electron imaging, x-ray microprobe analysis, and high resolution x-ray photoelectron spectroscopy (XPS) as illustrated as an example in figure 3 and figure 4. Figure 3 shows traces of lead compounds identified on the surfaces of mineral wool by XPS, and the analysis of x-ray photoelectron spectra led to the identification of two peaks containing either lead oxide or lead sulfate (figure 4). The presence of lead oxide on the surface of mineral wool indicates the existence of extremely high temperatures during the collapse which caused metallic lead to volatilize, oxidize, and finally condense on the surface of the mineral wool [1].

The temperature required to volatilize/boil lead is 1,740 C or 3,164 F [8]. No explanation for the origin of the indicated “extremely high temperatures during the collapse” is offered in the RJ Lee report.

4.3. Molybdenum spherule in the USGS data set

Two of the authors pursued a Freedom of Information Act (FOIA) action with the USGS to obtain any additional SEM/XEDS data from them which had not been previously published. The new data demonstrated, significantly, that the USGS team had observed and studied a molybdenum-rich spherule which was not mentioned in the earlier reports. A micrograph image shows a bright pill-shaped spherule labeled “20MOSPH1.TIF” (below). The brightness of the object suggests that backscattered electron imaging was used in acquiring the image (the report notes that this technique was used in the study), and that indeed a heavier metal such as Mo is present in the oblong spherule. (We see similar shapes; see SEM image below right and Fig. 1.)

In the same data set obtained via FOIA action, an XEDS spectrum labeled “Molysph.TIF” and two nearly identical XEDS curves (with additional elemental identifications) labeled “Molly spectrum 25 kV” accompany what we deduce applies to the Mo spherule, given the designations. One of the spectra extends to approximately 19 keV (the electron beam energy was no doubt 25 kV), and shows a clear Mo line at 17.3 keV. This removes ambiguity regarding the peak at ~2.3 keV, which could otherwise be S or Pb or Bi (for example). The XEDS plots for this spherule labeled “Moly sph” show significant concentrations of aluminum, oxygen and calcium in addition to the dominant molybdenum peak and deserve further investigation. (For example, the Mo/Al peak height ratio is Mo:Al :: 5:1.)

We discern that considerable study was performed on this Mo-rich spherule, given the number of images and XEDS plots for it, yet these data were not previously released in the public USGS reports.[2] We emphasize these data because of the extremely high melting temperature of molybdenum, and the observation of this molybdenum-rich spherule. Molybdenum is a refractory metal known for its extremely high melting point [9]. Mo melts at 2,623 °C (4,753 °F) [10], although addition of other elements may lower the melting point. No explanation of the high temperature needed to form the observed Mo-rich spherule is given in the USGS material (either published or obtained by FOIA action).

4.4. Materials from WTC with a “Swiss-cheese appearance” corroborate high temperatures

Dust particles from the WTC collapse show a “Swiss cheese appearance as a result of boiling and evaporation,” as reported in the RJ Lee report:

Additionally, WTC Dust can be differentiated from other building dust on the basis of its unique composition and morphology. WTC Dust Markers exhibit characteristics of particles that have undergone high stress and high temperature. Asbestos in the WTC Dust was reduced to thin bundles and fibrils as opposed to the complex particles found in a building having asbestos-containing surfacing materials. Gypsum in the WTC Dust is finely pulverized to a degree not seen in other building debris. Mineral wool fibers have a short and fractured nature that can be attributed to the catastrophic collapse. Lead was present as ultra fine spherical particles. Some particles show evidence of being exposed to a conflagration such as spherical metals and silicates, and vesicular particles (round open

porous structure having a Swiss cheese appearance as a result of boiling and evaporation). -Materials transformed by high temperature (burning). These transformed materials include: spherical iron particles, spherical and vesicular silicates, and vesicular carbonaceous particles. These heatprocessed constituents are rarely, if ever, found together with mineral wool and gypsum in “typical” indoor dusts [1].

The RJ Lee report provides an image of a “vesicular alumino-silicate particle” which exemplifies the “round open porous structure having a Swiss cheese appearance as a result of boiling and evaporation” (below, left). [1] The images below “show the difference between an angular non-porous non-heat affected particle within a Background Building [right] and a porous WTC Dust silicate heat-affected particle [left]”.

It is not clear to us that boiling of aluminosilicate is needed to produce the observed porous structure; melting and evaporation of some minor component may suffice. But if the “Swiss-cheese appearance” is indeed a result of “boiling and evaporation” of the material as the report suggests [1], we note the boiling temperature for aluminosilicate is approximately 2,760 °C [11].

The phrase “Swiss cheese appearance” was also used by a team from Worcester Polytechnic Institute led by

Prof. Jonathon Barnett in describing steel from WTC 7. The significance of the work on a [steel] sample from Building 7 and a structural column from one of the twin towers becomes apparent only when one sees these heavy chunks of damaged metal. A one-inch [steel] column has been reduced to half-inch thickness. Its edges--which are curled like a paper scroll--have been thinned to almost razor sharpness. Gaping holes--some larger than a silver dollar--let light shine through a formerly solid steel flange. This Swiss cheese appearance shocked all of the fire-wise professors, who expected to see distortion and bending--but not holes [12].

The researchers argue that a eutectic formed at approximately 1,000 °C in this steel sample from WTC 7: A liquid eutectic mixture containing primarily iron, oxygen, and sulfur formed during this hot corrosion attack on the steel… The eutectic temperature for this mixture strongly suggests that the temperatures in this region of the steel beam approached 1,000 °C (1,800 °F), which is substantially lower than would be expected for melting this steel [13].

However, to form a molten iron-oxygen-sulfur eutectic at about 1,000 °C would require a very high concentration of sulfur, around 50 (mol. %) [14]. ]. The fact that sulfur evaporates at a low temperature, 445 °C, along with the very low levels of elemental sulfur in office buildings appears to preclude the possibility that the eutectic could have formed as a result of a slow sulfidation process in the debris pile. In any case, the authors admit that

The severe corrosion and subsequent erosion of Samples 1 [WTC7] and 2 [Towers] are a very unusual event. No clear explanation for the source of the sulfur has been identified [13].

Nevertheless, we will provisionally accept their analysis that a steel (not air) temperature of about 1,000 °C was reached, pending understanding of the source of the observed sulfur. (The XEDS plots shown by the authors show sulfur without concomitant calcium, which would be present for a calcium-sulfate (gypsum) contamination.) [13] The other data summarized here point to significantly higher temperatures than 1,000 °C.

It is interesting that the FEMA report discussed the “evidence of a severe high temperature corrosion attack on the steel, including oxidation and sulfidation” and called for further investigation, [13] – but the subsequent NIST report [15] failed to address this evidence. Nor did NIST address the published observations of abundant iron-rich spherules in the WTC dust [1, 2]. We find that these effects are important to understanding the events of 9/11/2001 and should not be neglected.

4.5. Summary of Temperatures Required by the WTC Data

The formation of spherules in the dust implies the generation of materials somehow sprayed into the air so that surface tension draws the molten droplets into near-spherical shapes. That shape is retained as the droplet solidifies in the air. Spherules observed in the WTC dust include iron-rich, molybdenum-rich and silicate varieties. The temperatures required to melt iron, silicates, and molybdenum, and to vaporize lead and aluminosilicates (as discussed above) are summarized in table 1.

Table 1. Approximate Minimum Temperatures Required

4.6 Maximum temperatures associated with the WTC fires

Finally, we consider the temperatures reached in normal building fires, jet-fuel fires and in the World Trade

Center buildings. Maximum temperatures due to fires in the WTC of around 1,000 C are argued by Thomas

Eagar: The fire is the most misunderstood part of the WTC collapse. Even today, the media report (and many scientists believe) that the steel melted. It is argued that the jet fuel burns very hot, especially with so much fuel present. This is not true.... The temperature of the fire at the WTC was not unusual, and it was most definitely not capable of melting steel. In combustion science, there are three basic types of flames, namely, a jet burner, a pre-mixed flame, and a diffuse flame.... In a diffuse flame, the fuel and the oxidant are not mixed before ignition, but flow together in an uncontrolled manner and combust when the fuel/oxidant ratios reach values within the flammable range. A fireplace is a diffuse flame burning in air, as was the WTC fire. Diffuse flames generate the lowest heat intensities of the three flame types... The maximum flame temperature increase for burning hydrocarbons (jet fuel) in air is, thus, about 1000 °C --hardly sufficient to melt steel at 1500 °C.

But it is very difficult to reach this maximum temperature with a diffuse flame. There is nothing to ensure that the fuel and air in a diffuse flame are mixed in the best ratio... This is why the temperatures in a residential fire are usually in the 500 °C to 650 °C range. It is known that the WTC fire was a fuel-rich, diffuse flame as evidenced by the copious black smoke [16].”

NIST provides a maximum gas temperature due to WTC fires of 1,000 °C:

In no instance did NIST report that steel in the WTC towers melted due to the fires. The melting point of steel is about 1,500 degrees Celsius (2,800 degrees Fahrenheit). Normal building fires and hydrocarbon (e.g., jet fuel) fires generate temperatures up to about 1,100 degrees Celsius (2,000 degrees Fahrenheit). NIST reported maximum upper layer air temperatures of about 1,000 degrees Celsius (1,800 degrees Fahrenheit) in the WTC towers (for example, see NCSTAR 1, figure 6-36) [17].

Based on this comprehensive investigation, NIST concluded that the WTC towers collapsed because: (1) the impact of the planes severed and damaged support columns, dislodged fireproofing insulation coating the steel floor trusses and steel columns, and widely dispersed jet fuel over multiple floors; and (2) the subsequent unusually large jet-fuel ignited multi-floor fires (which reached temperatures as high as 1,000 degrees Celsius) significantly weakened the floors and columns with dislodged fireproofing to the point where floors sagged and pulled inward on the perimeter columns [18].

In actual metallurgical analyses of WTC steel, NIST reports: These [steel] microstructures show no evidence of exposure to temperatures above 600°C for any significant time [18].

In a report entitled “Fire Safety in High-rise Buildings, Lessons Learned from the WTC,” a team of fire

experts notes: Standard structural fire testing exposes elements to about 900 °C in 1 hour and up to 1,100 °C by 4 hours. The expectation of these standard tests could well be defined as providing a worst-case fire scenario [19].

All of these estimates for the WTC fires (including burning jet fuel) put the temperature well below the

melting point of steel, about 1,500 °C [17]. In fact, the non-melting of WTC steel is emphasized by NIST – but

they fail to address the presence of large numbers of iron-rich spherules in the dust published in USGS and

other reports before the NIST study was published in October 2006 [16, 18].

Table 2 summarizes maximum temperatures determined for the WTC fires.

Table 2. Maximum Gas Temperature Reached in WTC Fires [20] Analysis °C °F