Mars Geology, Ancient Art, Lake Sediments

Another bunch of readings for you : 

1) Perseverance Can Continue To Operate On Mars Until At Least 2031- The gallant rover continues its exploration. How do NASA engineers plan a route and how do team geologists decide what to sample? Terrain consideration and rock outcrops are key and so far Perseverance has aced the challenges of topography and geology. Some beautiful maps too in this article.

2) Rock art from at least 67,800 years ago in Sulawesi- How do you date rock art? The material used, mineral pigments mostly, cannot be dated directly. Often, ancient cave walls are covered with layers of calcite precipitated from water seeping along the walls. This calcite can be dated as it contains radiogenic Uranium, giving us a minimum age for the underlying art.

Rock art from Sulawesi, Indonesia, have yielded minimum dates of around 67 thousand years ago. This makes it among the earliest rock art known anywhere. Also, the location of Sulawesi, separated from Bornea by wide deep water channels, suggests that the initial peopling of Sahul around 65k involved maritime journey from Borneo to Papua. Modern Homo sapiens first reached this region sometime after 60,000 years ago.

Who then made this art? Denisovans, or some other branch of humans? The Indonesia- Papua region with an improving fossil and material record of being populated by a variety of humans is proving to be a very important area to understand human migrations and evolution.

3) Sediments reveal 2,600-year-old story of human persistence in central India- Desilting of lakes is going on in many parts of India. I say, before the JCB’s move in , send in the climate scientists. Sahana Ghosh writes about some fascinating work from the wetlands of Bandhavgarh forests in Central India. Scientists have reconstructed a climate and ecologic history going back 2600 years from lake sediment and then matched that with human cultural and political changes. Even as climate changed, humans adapted and modified landscapes. This is one of the few paleoclimate archives from Central India.

Links: Noisy Soils, First Art, Mars Geology

A few readings for your perusal.

1) Biologists are poking senors into soil to listen to the hum of life. Amazing article by Ute Eberle on what we can learn from acoustic signals given off by animals living within a soil profile.

Life in the soil was thought to be silent. What if it isn’t?

2)  When was the first 'árt' made? Is there a neat sequence from abstract scratches on rock and bone to representational art that adorns the walls of caves? Excellent article by Amy McDermott on this question, bringing together the viewpoints of archeologists and cognitive scientists. 

What was the first “art”? How would we know?

3) One year on, NASA's Mars Perseverance has been drilling into rock, collecting samples and finding some surprises along the way. It will now head towards an ancient delta to look for past life! Alexandra Witze reports on the progress.

A year on Mars: How NASA’s Perseverance hit a geological jackpot.

 

Links: Petroglyphs, Language, Urban Groundwater, Dams

Some interesting articles I came across past few days.

1) Pleistocene Rock Art in India- New York Times covers the discovery of ancient rock art (40k-10K yr old?) carved on laterite plateaus of Ratnagiri District, S. Maharashtra. Good to see credit given to the stellar work of two amateur archaeologists Sudhir Risbud and Dhananjay Marathe.

Link: Ancient Rock Art In The Plains Of India.

2) Language Evolution- Linguistic analysis suggests that the Sino-Tibetan language family originated about 7200 years ago among millet farming communities in northern China.

Links: Paper - Dated language phylogenies shed light on the ancestry of Sino-Tibetan.
Summary - Origin of Sino-Tibetan language family revealed by new research.

3) Urban Groundwater- This is an issue that is gaining importance as cities in India grow and municipal water supply from surface reservoirs becomes inadequate. S. Vishwanath crunches some numbers on the ground water potential of the shallow aquifer underneath Bengaluru. It comes to more than hundred billion liters! Similar situations exist underneath other Indian cities as well, but urban groundwater has been a neglected area of study. More quantitative understanding of aquifers is needed along with a focused effort to recharge ground water.

Link:  Revisiting The Shallow Aquifer. 

4) Environmental Implications of Pancheshwar Dam, Uttarakhand - A review in Current Science of environmental concerns regarding the proposed Pancheshwar Dam in Uttarakhand implies that critical aspects of seismicity, slope instability, and high sedimentation rates have not been addressed in detail during the planning stages in the environment impact assessments carried out so far.

Link: Environmental implications of Pancheshwar dam in Uttarakhand (Central Himalaya), India.

Dating Rock Art

I love it when science is explained with a well thought out and cleanly drawn illustration.

A commentary in Nature News and Views by David G. Pearce and Adelphine Bonneau presents this diagram on dating rock art.

Two recent studies on dating cave paintings from Spain are discussed.

Who were the artists?

The oldest minimum age for the paintings is 66 ka (thousand  years) leading to speculation that they might have been drawn by Neanderthals. The earliest presence of modern humans in Spain is from  40 ka. This would imply independent evolution of symbolic behavior in Neanderthals.  However, the same painting throws up a range of minimum dates from ~ 60 ka to ~ 3 ka making an exclusive link  to Neanderthals problematic.

Imagination And Art In The Cave Of Forgotten Dreams

Filmmaker Werner Herzog got a once in a lifetime opportunity to enter the Chauvet caves in France which has some exquisitely preserved rock paintings, dated to about 30 thousand years ago. He made a 3D movie of the interior of the cave.

On Fresh Air he talks about his experience:

GROSS: And they wanted you to keep on the walk so that you didn't contaminate the rest of the cave, yeah.

Mr. HERZOG: Oh, you never - can never touch anything. It's not just contaminating. There are footprints, fairly fresh footprints. You do not want to superimpose your print of your hiking boot upon it. There's...

GROSS: Oh, over the cave-bear print. Yeah. 

(Soundbite of laughter) 

Mr. HERZOG: Yes, you just don't do this. And there's a footprint of a child, maybe eight-year-old, this very mysterious. We couldn't film it. We were not allowed, because it was deep in the recess of the cave.

The mysterious thing is that next to this footprint, probably a boy, probably around eight years old, parallel to it runs the footprint of a wolf. And I was very, very puzzled: Did the wolf stalk the boy? Or did they walk together as friends? Or did the wolf leave its footprints 5,000 years later? It's stunning. The lapse of time is completely and utterly stunning.

 
What a context for an artist to let loose his imagination! The Cave of Forgotten Dreams indeed.. but also the Cave of Infinite Imagination.

Werner Herzog also recently joined physicist Lawrence Krauss and author Cormac McCarthy in a conversation about how science and art inspire each other. Speaking about the differences between art and science Krauss remarks:

Science is imagination in a straitjacket.

Not quite so for the artists in the Cave Of Forgotten Dreams.

Listen / Transcript

Buddhist Rock Cut Monuments And Deccan Lava Flows

During my recent field trip to the Konkan west coast one of the geologists leading the trip mentioned that all the famous Buddhist rock cut monuments situated in the Deccan volcanic province were excavated in lavas of the Bushe Formation.

I had never given any thought to this before. If you look at the various famous Buddhist rock monuments...Ellora, Ajanta, Bhaja, Karla, Elephanta ...they do occupy  similar looking basalt slopes and escarpments. Those are the lavas belonging to the Bushe Formation confirmed the geologist.

The Deccan Basalt lava pile is subdivided into hierarchical geological units - each corresponding to an eruptive episode - based on their geochemical similarities. Here is the basic chemical stratigraphy:

The Bushe Formation is quite thick and made up of compound lava flows. That means that eruptive episodes were made up of blobs of lava units that spread and overlapped and coalesced with other lava units to form a compound unit, forming a humpy undulating lava pile in the process.

Like a overlapping stack of pancakes...like this one..with the Bushe Formation for comparison..

So why did Buddhist monks and artisans choose these lava flows out of the many rock slopes and escarpments from other lava flows available..?

My quick speculations:

1) East of the Western Ghat escarpment is the Deccan plateau which is dissected into spurs of Deccan Traps and flat valleys. The Bushe Formation is well exposed in these spurs forming slopes and thick rock escarpments.

2) The locations of the caves in this part of the Deccan where the Bushe Formation is prominent are along ancient trade routes. Patronage from sympathetic merchants and rulers provided sustenance for the monks and artisans.

3) The Bushe Formation occupies a convenient middle tier in the multi-storey Deccan landscape.

Landscape evolution has transformed the Deccan lava pile in to a series of steep slopes and escarpments. The Bushe Formation especially the escarpments are situated above forested slopes which grade into the valley floors. That would have made Bushe escarpments ideal locations... isolated enough from the roads and villages to suit the Buddhist monastic lifestyle but still accessible via the forested slopes. Many of these caves also acted as resting stops for traders and merchants and so making them not too inaccessible by going too far up the landscape might have been a consideration.

Here is a picture of the Bhaja caves near Pune...occupying a steep rock slope.

Formations younger than Bushe form the upper story escarpments of the Deccan landscape. Access to these may have been too tough to negotiate.

4) The workability of the rock material.

Maybe there is a difference in the way rock material of the Bushe gives way to hammers and chisels compared with other especially the younger lavas. The Bushe has been described as a blocky kind of a lava while the younger lava which also form escarpments have been described as having splintery properties that may not give way to form the rounded and blocky shapes the artisans wanted.

I don't know. This is a problem that some experimental Archaeology can throw light on.

These rock-cut monuments are a wonder. If you are in the area don't miss out visiting them.

Images of Alzheimer's

An article in Science Daily about Alzheimer's caught my eye. Brain imaging is rapidly evolving into a powerful tool to diagnose various types of brain disorders. In this study, a positron emission tomography (PET) scan of sugar uptake by the brain allows a more accurate diagnosis of a type of dementia frequently mis-diagnosed as Alzheimer's. This will allow for earlier detection and better treatment of dementia. Modern imaging methods like PET and Magnetic Resonance Imaging (MRI) allows us to peek into our brains and observe the effects of the disease. In multicolor these images can show loss of brain tissue as with MRI and patterns of metabolism as with PET. But these images are clinical. They don't portray the emotional turmoil the patient must be going through, the sense of loss and a steady inexorable distancing from the familiar world. How can a machine capture this personal catastrophe? I was reminded of a different kind of image of Alzheimer's in an article I read several years ago.

In 1997 artist William Utermohlen, was diagnosed with Alzheimer's when he was 60 years old. He captured the ravages of the disease in a series of haunting self-portraits. Soon after his last sketch in 2000, the artist stopped painting. He is now in a nursing home.

1996-1997

1997-1998

1999-2000

Galerie Beckel Odille Boicos, Paris

A picture is worth a thousand words. So true!