Context: Recently, the 56,000-year-old Lonar crater sanctuary lake in Buldhana district has turned dark pink. Lonar Lake is famous as the world’s Largest Basaltic Impact Crater.
Background

• Similar phenomenon of the water in the lake turning dark pink takes place in Umria lake in Iran.
• during dry seasons, water level goes down, thus increasing the salinity of water and making it warm too.
• This becomes the breeding ground for Dunaliella algae- which under such circumstance, turns red in colour.
• The halobacteria also uses a red pigment to absorb sunlight and convert it to energy.

Key Findings

• The lake is reported to be highly alkaline in nature with a pH of 10.5, but is also unique for its high levels of salinity.
• The strange geochemistry of soda lakes enables the growth of specific types of microorganisms, some of which are not found anywhere else.
• Lonar Lake is designated as a national geo-hertiage monument, and regarded as the world's largest basaltic impact crater
• Scientists have hypothesised that the phenomenon may be caused by the growth of a family of bacteria known as Halobacteriacaeae.

About Lonar Lake

• Lonar Lake, also known as Lonar crater is a saline, soda lake, located at Lonar in Buldhana district, Maharashtra.
• It is a notified National Geo-heritage Monument.
• Lonar Lake was created by an asteroid collision with earth impact during the Pleistocene Epoch.
• It is one of the four known, hyper-velocity, impact craters in basaltic rock anywhere on Earth.
• The other three basaltic impact structures are in southern Brazil.

About Halobacteriaceae

• They are found in water saturated or nearly saturated with salt. They are also called halophiles, though this name is also used for other organisms which live in somewhat less concentrated salt water. 
• They are common in most environments where large amounts of salt, moisture, and organic material are available. 
• Large blooms appear reddish, from the pigment bacteriorhodopsin. This pigment is used to absorb light, which provides energy to create ATP(Adenosine triphosphate).
• Halobacteria also possess a second pigment, halorhodopsin, which pumps in chloride ions in response to photons, creating a voltage gradient and assisting in the production of energy from light. 
• The process is unrelated to other forms of photosynthesis involving electron transport; however, and halobacteria are incapable of fixing carbon from carbon dioxide.
• Halobacteria can exist in salty environments because although they are aerobes, they have a separate and different way of creating energy through use of light energy. 
• Parts of the membranes of halobacteria are purplish in color and contain retinal pigment. 
• This allows them to create a proton gradient across the membrane of the cell which can be used to create ATP for their own use.