October 11, 2019 (updated October 11, 2019)
Published by Gayathry
The lakes on Earth turn salty on drying out and the same incident happened when the Curiosity Mars climbed to identify the younger rocks. It found some of the salts which were left behind gathering insights on life could have prospered, rather than the mere survival on Mars. Gale crater was selected in part as it provides the possibility to investigate sedimentary rocks of different ages layered on top of each other. Curiosity has found periodic clay-bearing deposits containing 30-50 percent calcium sulfate by weight as reported in a Nature Geoscience paper.
All the rocks are 3.3-3.7 billion years old dating to the Hesperian period. Likewise, rich deposits have not been found in the older rocks of the crater. According to Dr. William Rapin of the California Institute of Technology and co-authors, the salts are present due to the percolation in the rocks by the waters of the bygone lakes which were very salty. Older rocks were much less salty although they were also exposed to the waters. Curiosity might detect more recent examples even though the younger ones were never touched by water.
Like a desert lake on Earth, the waters of the Gale crater evaporated, leaving a saltier residue, but it was an intermittent process on Mars that lasted 400 million years. The rocks have been subjected to forces of weathering over this vast time period even without water, and the calcium sulfate-enhanced portions are more resistant to erosion, producing mini versions of the formations in places such as Monument Valley, where harder rocks extend above the terrain.
Curiosity found a 10-meter (33-feet) slope containing 26-36 percent magnesium sulfate, in the 150 meters (500 feet) of calcium sulfate-enriched layers. Researchers believe that before the deposition of more soluble salts, it precipitated out first.
The paper mentions that their outcomes do not compromise the life search in the Gale crater. Terrestrial magnesium sulfate-rich and hypersaline lakes are known to sustain halotolerant biota while the preservation of biosignatures may be supported by crystallization of sulfate salts.
The occasional bursts of salty water are observed even today hence it is not unique to Gale crater in having such salts. As the planet dried, sulfate deposits have been identified by Martian orbiters across several places on Mars and it is the first instance where a rover has been operated its instruments over these samples. The periodic bursts of sulfate salts found by Curiosity showed Gale crater had many rounds of drying with several wet periods rather than one single great drought.
Journal Reference: Nature Geoscience
September 5, 2019
Published by Sai Teja
- A properly designed material which is made of calcium phosphate ion clusters can be used to create a precursor layer for inducing the epitaxial crystal growth of enamel apatite.
- This needed a new type of calcium phosphate ion clusters which had a diametrical measurement of 1.5 nanometres. They were stabilised in ethanol with the help of triethylamine
Tooth enamel is the hardest substance in our body. It is irreplaceable and many people all over the world suffer from tooth decay due to loss of enamel. However new studies offer hope to end this problem.
Researchers in China have come up with a liquid solution which can help in growing back the outer surface of the damaged tooth enamel with the help of a material which mimics the mineralisation process of the protective outer layer of our teeth. The work appears in Science Advances journal.
Tooth enamel is created in a biomineralisation process where cells known as ameloblasts generate proteins which harden to form the tough outer coating of our teeth. But ameloblasts are only present during the course of tooth development as a result of which the mature teeth cannot repair itself after its formation.
Researchers have tried several approaches to coax enamel remineralisation artificially but they have mostly failed since the crystalline structure of the enamel has not been properly replicated in the laboratory. Zhaoming Liu, biomimetics and materials researcher said that in this new technique they reveal that a properly designed material which is made of calcium phosphate ion clusters can be used to create a precursor layer for inducing the epitaxial crystal growth of enamel apatite. This mimics the biomineralisation crystalline-amorphous frontier for the development of hard tissue.
This needed a new type of calcium phosphate ion clusters which had a diametrical measurement of 1.5 nanometres. They were stabilised in ethanol with the help of triethylamine which avoided them being clumped together. They were then applied to the human teeth which were donated by the patients. The super-small clusters properly fused to form the fish scale-like structure of native enamel. This replicated the tooth coating with an equally hard layer which had a thickness of 2.8 micrometres in 48 hours.
That is very much thinner compared to the full layer of normal tooth enamel, however, researchers feel that repeated coatings of CPIC solution could increase the thickness along with further refinements. Liu said that that generated enamel has the similar structure and properties to that of native enamel. Researchers hope to generate tooth enamel without fillings that contain entirely different materials. They are expecting to begin trials within one to two years.
To meet the deadline, scientists have to prove that the material is safe as presently there are concerns regarding the toxicity of triethylamine, which is the stabilising compound. It evaporates during the process hence should not be of any risk. The substance is currently being tested in mice. It might take some time before it is adopted for daily use and till then the conventional advice on dental health has to be followed. Chen Haifeng, Peking University who was not part of the study thinks artificial replacement can never properly replicate the natural teeth.
Journal Reference: Science Advances journal