Maxime Boccas1,5, Patricio Bustamante Díaz2,5, Carlos González Vargas3,5, Carlos Monsalve Rodríguez4,5

1 Cerro Tololo Inter-American Observatory, La Serena, Chile, mboccas@noao.edu

2 Comisión Nacional de Energía, Santiago, Chile, ing.con@entelchile.net

3 Instituto de Estética, Pontificia Universidad Católica de Chile, Santiago, cgonzale@puc.cl

4 Instituto de Arte y Comunicación Social (Arcos), Santiago, Chile

5 Intijalsu Ltda., Castor Villarin 35, Santiago, Chile, http://www.oocities.org/intijalsu/

2.3. Pucará de Lasana (II Region)

2.3.1.Introduction

The pucará de Lasana (22°18' S, 68°39' W, 2256m) is located in the Loa river canyon in the Atacama region near the town of Calama. This area was inhabited by the Atacameña culture, through successive stages, from 400 B.C. until the Inca conquest in 1471 A.D. The Pucará de Lasana is one of several settlements (Quitor, Turi) built around the XII century. Lasana is one the largest and best-preserved pre-Colombian villages in the North of Chile. Among the hundreds of rooms spread along 250m of constructions, only one features windows with a non-rectangular shape. We identified interesting effects created by rays of sunlight going through these apertures that have a calendaric function.

2.3.2. Anthropological context

Since the III century A.D., Tiwanaku had created the greatest empire in the central Andes which lasted until the XI century when some terrible droughts collapsed the highly-productive agricultural system developed around the Titicaca lake and led to the progressive social and political disintegration of the empire. The level of influence of Tiwanaku on the Atacameña culture, mainly through commercial exchanges of the various minerals (copper and various precious stones) being extracted from the desert soil, peaked in the VIII century. Berenguer and Dauelsberg (1997) published an extensive overview of this subject. Toward the end of Tiwanaku's era, several small kingdoms surged in the altiplano and some twenty pucarás were built between Arica and San Pedro de Atacama and reflect the many local conflicts happening at that time (Schiapacasse et al. 1997). Lasana is built on a north-south rocky ridge in the middle of the Loa river canyon (500m wide and 100m below the altiplano level in that area). The pucará architecture is varied: it contains habitation-type rooms (walls are up to 2-3m high, made of small arenisca stones bonded together with mud), storehouses, tombs and possibly an industrial sector where the red ceramics (Lasana style) were manufactured, and then distributed in most of the region. Outside of the pucará, large terraces were organized for agriculture, allowing to feed some 500 to 800 people. The site has been cleaned up and partly reconstructed in the years 1951-53 by Montandón (1950). Very few complete descriptions and analysis of the site are found in the literature. In recent years, several anthropologists have investigated in this region. We will mainly refer to the work of Van Kessel (1996) who focused on the Aymara cosmovision and their spatial division of the world:

· Arajpacha: the sky and the space beyond, inhabited by God and the Sun;

· Acapacha: the local world and mountains, inhabited by Mallku (condor), Pachamama (puma, lizard, toad) and Mallku (snake, fish);

· Manqhapacha: the hell, inhabited by devils.

The author mentions briefly the time division they used: a solar year divided in two parts by the solstices, and a climatological year divided in dry, rainy and cold seasons. The two groups forming the active population, the shepherds and the farmers, get to cohabit and work together during the autumn and winter: at the end of March, the pastors bring their herd down to elevations of 2000-2500m until September-October when they go up to the altiplano again (4000m). Each group of the population has its own feasts at a times roughly opposite in the year: the shepherds celebrate successively their constructions (October-November), the fertility of their herd (December-January when the camelidae have their youngs) and the mountains ("fiesta del Mallcu" early February); and the farmers celebrate the harvest ("Cruces de Mayo" early May when people build their roofs using the straw freshly cut and next decorate them with a cross), fertility of the lambs (end of June) and fertility of the Earth by cleaning out the irrigation channels of their fields (early August). Amaru, the snake deity, is associated with that latter time for fertility reasons. During that ritual, the farmers have to ask permission of the volcanoes, the guardians of the ground. People actually establish a difference between mountains, born when the stars came down to the earth, and the volcanoes, which regulate the functioning of the Earth (wind and storms, water and rain, freezing). August is also the time when the farmers organize supplication ceremonies to the rain and start planting (it can last four months).

2.3.3. The calendar room

All habitations (and storehouses) in the pucará are fitted with rectangular doors and windows, except one. In the 1950's, Montandón had noticed the cross-shaped windows of one room and qualified it as the room of the village chief. In 1971, González borrowed the pucara's drawings and started investigating the interaction with the light by making models. In 1988, he was able visit the site at the date he had calculated and confirmed his theory, later improved during other trips. Here, we don't provide many more new details, but rather do a more systematic presentation and suggest a few investigation paths.

González (1992) published some conclusions about this singular room (figure 6) whose western wall is opened with 2 similar cross-shaped windows (W1 and W2 on figure 7) located 1.5m apart from each other and 2m above the ground (figure 7). The cross arms are about 30 cm long and 10 cm wide. During a few days around the 6th of February and the 6th of November (dates half-way between the summer solstice and the equinoxes), both rays of light, entering the room through these windows, hit the ground at the bottom of the northern wall and end their trajectory by ascending the northern wall to die at sunset respectively in the two niches N1 and N2 (holes made in the wall made by intentionally leaving out a stone). The sunset light spots move about 3cm centimeters every day, thus framing fairly well the central date within +/- 1 day. The beauty of the effect is reinforced by the presence of two windows and not just one. We don't understand yet the meaning and the need for such a double alignment although we can invoke some kind of dual living principle (masculine and feminine) frequent in ancient mythologies. We shall also say that the date pointed out by the alignment is mysterious to us because, in modern calendars of the Aymara people living in the San Pedro area, no specific celebration or activity is held at these dates. We can formulate hypothetical and naive reasons, like the need to represent both passages of the sun through that date or the desire to commemorate the birth of twin sons, an understandable sign of affection for a family of important people.

Six months after these dates, roughly on the 6th of August and the 6th of May (in between the winter solstice and the equinoxes), the beam of light going through W1 ends its path, at the sunset, in the direction of the foot of a square pillar (figure 6) located inside the room toward the eastern wall. No logical reason can be proposed for the location of this construction but the alignment with a specific date in a solar calendar. Early August, one could think that when the sunlight comes toward the center of the pillar, it indicates time for a celebration related to the call for fertility of the Earth. In July and August (usually) snow happens to fall in large quantity above 3500 of elevation. This snow will fertilize the Earth for most of the year through all the water that it will feed into the streams and rivers. In the very arid Atacama desert, water is by far the highest necessity for surviving; thus it is very likely that any ancient calendar would have also privileged ritual ceremonies related to water, rain and snow.

In any case, these alignment dates comes to frame perfectly the solar annual cycle with the northern wall alignment in the niches. The pillar, about 1m high (nowadays), could have served as an altar for sacrifices or adoration of a ritual ornament. The other important characteristics of this pillar is its extreme surface smoothness, squareness and verticality compared to any other stone structures in the pucará. This observation leads us to suggest the altar was also used as a gnomon for monitoring the zenith passage of the sun, which occurs 18 days before and after the summer solstice. We tried out the nadir (anti-zenith) passage hypothesis, which would have occurred around the 26th of May and 2nd of July in the year 1200, but couldn't associate it with any features in the masonry.

To conclude the description of the effects related to the windows W1 and W2, it is worth mentioning another particular geometrical effect: at the time of both solstices, the rays of light enter these windows in a very oblique way and the sun gets to project S-shaped spots of light on the walls, curiously simulating a snake (any relation to the god Amaru?) sliding on the stones. At some moments, one could even see the luminous shape of a llama with a bit of imagination. Was the intention in shaping the windows like crosses to project spots of light with a symbolic appearance? The cross shape was found by a few investigators on textiles of Lasana and the San Pedro area but not on ceramics. We intend to investigate more thoroughly the recurrence and meaning of this shape, probably associated to the more general concept of the Andean cross.

The room exhibits another intentional architectural feature related to solar illumination. The northern wall is perforated by 2 windows, about 25cm square and roughly 7m apart, which are not perpendicular to the wall thickness: they are oblique and their respective axes intersect exactly at the doorstep A. From there, an observer can actually observe a very small area on each of the ridges of the Loa canyon, precisely where pathways allow one to come down to the river. It appears the design was made to allow surveillance of key accesses to the pucará. Besides that particularity, the light of the winter solstice rising sun penetrates W4 and dies in the middle of the doorstep A! Again, we don't know yet the meaning of that alignment but, added to the other calendarical features described previously, it is certainly not the fruit of hazard.

2.3.4. Conclusion

We have presented a strong case for intentional astronomical orientation in the masonry of a construction of the San Pedro culture, dating back to the XII century approximately. Because of the multiple effects orchestrated in a single room, and leading to the determination of specific dates in the solar cycle, we conclude that the social structure of the village probably included a priest, a sun-watcher, in charge of organizing temporally the activities of the community. The case is still very intriguing because the dates emphasized do not correspond clearly to rituals still in practice today. Thinking about the impact of a total solar eclipse among the ancient people, and whether a repeated occurrence of them (see Liller 1986) could have triggered a deeper adoration or respect to the Sun, and the actual construction of a room dedicated to solar observation, we searched noticeable solar eclipses (i.e. total, partial or annular with obscuration >95%) from Lasana between 900 and 1400 A.D., and found the following events:

- X century: 3 (945: 4 min. totality, 960: partial, 999: 6 min. totality),

- XI century: 0

- XII century: 3 (1112: 2 min. totality, 1163 and 1198: partial)

- XIII century: 2 (1224: partial, 1292: 6 min. totality),

- XIV century: 2 (1337 and 1372: partial)

We are especially attracted by the combination of the eclipses of the X century: the first and the last ones are long and very long (in "eclipse jargon") and the three of them happened rather closely in time (44 years). We don't know if a link will ever be made between this fact and the characteristics of Lasana (or another site nearby) but we think it is worth having this element in mind when evaluating the relationships between the Atacameña culture and the sky (as it would be for any cultures by the way). As a matter of fact, we have not yet explored in depth the other pucarás of the region in search of similar astronomical designs but the discoveries made at Lasana certainly opens up an interesting window to archaeo-astronomical investigation among the Atacameña culture. To follow that path, one should keep in mind the strong intellectual influence of Tiwanaku present in Northern Chile (Lasana is an exception because the site and the material excavated don't reveal any connections with the Titicaca-based empire).

Figure 6

Figure 7