Lonar Lake: India’s Only Meteorite Impact Crater Lake

Lonar Lake, located in Buldhana district of Maharashtra, is a unique geological feature — India's only known meteorite impact crater lake and one of the few in the world formed by a basaltic rock impact. Formed approximately 52,000 years ago when a meteorite slammed into the Deccan Plateau, Lonar Lake is simultaneously saline and alkaline — a rare combination that supports unique microbial life and has fascinated scientists for over 170 years.

For UPSC, Lonar Lake is a frequently tested Geography and Environment topic — especially after its dramatic pink colour change in 2020 brought it international attention.

Formation

Meteorite Impact

Lonar Lake formed when a meteorite estimated at 2 million tons struck the Deccan Trap basalt rock at speeds of approximately 90,000 km/h:

• Time of impact: Approximately 52,000 years ago (estimates vary between 35,000-570,000 years)
• Impact energy: Equivalent to a 6 megaton hydrogen bomb
• Crater depth: Original depth ~500 m; current visible depth ~150 m (with lake water)
• Crater diameter: ~1.8 km
• Rim height: ~20 m above surrounding terrain

Why Unique

Lonar is one of only four known meteorite impact craters in basaltic rock worldwide. Others include:

• Lonar (India) — basaltic
• Manicouagan (Canada) — partial
• Most known craters are in sedimentary or granitic rock
• Basaltic craters are rare because basalt is hard and melts/vaporizes differently under impact

This makes Lonar a natural laboratory for understanding:

• Impact dynamics in different rock types
• Conditions similar to other planets (Mars, Moon — which have basaltic rocks)
• NASA and ISRO scientists have used Lonar for analog studies of extra-terrestrial craters

Historical Debate

The impact origin was not immediately accepted. Scientific theories over time:

• Volcanic (proposed by British geologists in the 19th century)
• Explosive (by Indian scientists in the early 20th century)
• Meteorite impact (proven in the 1970s through analysis of quartz deformation, iridium anomalies)

Final proof came from shocked quartz crystals found in the crater rim — only possible through meteorite impact.

Geographic Location

The lake lies approximately 160 km east of Aurangabad, accessible by road.

Water Characteristics

Lonar's water has unique chemical properties:

Saline-Alkaline Composition

Most natural lakes are either saline OR alkaline — Lonar being both is unusual. This creates:

• Unique microbial communities (halophiles and alkaliphiles)
• Unusual chemical reactions
• Distinct coloration under certain conditions

Water Sources

The lake has no surface inlet — it is fed by:

• Groundwater seepage
• Small streams during monsoons
• Has two named streams: Purna and Penganga (not the major rivers of the same name)

No surface outflow either — makes it an endorheic (closed basin) lake.

The 2020 Pink Colour Change

In June 2020, Lonar Lake dramatically changed colour from green to bright pink-red, attracting global attention:

The Phenomenon

• Sudden change observed over ~48 hours
• Covered much of the lake's surface
• Colour was striking pink to deep red

Scientific Explanation

The pink colour was caused by a combination of:

• Halophile and haloalkaliphile bacteria (like Halorubrum) — produce pigments under stress
• Algal bloom of pink-pigmented species
• Sulphate-reducing bacteria activity
• Evaporative concentration due to high summer heat and reduced rainfall
• Low water levels creating high salinity stress

Similar phenomena occur in:

• Lake Hillier (Australia) — permanent pink colour
• Salton Sea occasional pink events
• Lake Urmia (Iran)
• Lake Retba (Senegal) — Lake Rose

Duration

Lonar's pink colour:

• Persisted for several weeks
• Returned to normal colour after monsoon rains diluted the lake
• Was recorded extensively by scientists for future study

This event was unprecedented in recorded history at Lonar.

Biodiversity

Despite harsh chemical conditions, Lonar supports remarkable biodiversity:

Unique Microbial Life

The lake's saline-alkaline waters host organisms found in few other places:

• Halophilic bacteria (Haloarchaea)
• Alkaliphilic bacteria
• Sulphate-reducing bacteria
• Cyanobacteria (blue-green algae)
• Multiple novel species discovered only at Lonar

Macro-biodiversity

Habitat Significance

• Stopover for migratory birds including pelicans, flamingos
• Important site for ornithology
• Designated as a Wildlife Sanctuary by Maharashtra

Temples Within and Around the Crater

Lonar crater is also a significant religious site with ancient temples dating from the Chalukya period (10th-12th century CE):

The temples are built of basalt and showcase classical Chalukya architecture. They are relatively well-preserved given their age.

Conservation Status

Protection

• Wildlife Sanctuary — designated by Maharashtra government
• Notified as Ramsar Site — in November 2020 (India's 41st Ramsar Site at the time, now one of 85)
• National Geological Monument — designated by Geological Survey of India
• Protected under the Wild Life (Protection) Act, 1972

Threats

Despite protection, Lonar faces threats:

• Encroachment around the crater rim
• Groundwater depletion — affects lake water level
• Pollution from surrounding agricultural runoff
• Tourist pressure — ~500,000 visitors annually
• Temple waste — religious offerings polluting the water

Conservation Efforts

• ASI (Archaeological Survey of India) protects the temples
• Maharashtra Forest Department manages the sanctuary
• Scientific monitoring by multiple research institutions
• Ramsar Site status provides additional protection

Scientific Research

Lonar has attracted significant research interest:

NASA Studies

• Analog site for Mars research
• Mars's Gusev Crater (where the Spirit rover landed) has basaltic conditions similar to Lonar
• Helps understand microbial survival in extreme environments

ISRO Involvement

• Space research using Lonar as an analog site
• Chandrayaan-2 and Chandrayaan-3 mission planners studied Lonar for lunar crater analogs

Ongoing Research

• Impact dynamics studies
• Microbial biology research (novel species discovery)
• Climate change indicators — Lonar's chemistry responds to climate
• Astrobiology — implications for life in extreme environments

UPSC Relevance

GS1 (Geography): Unique geological features, lakes, Deccan Plateau geology.

GS3 (Environment): Biodiversity, conservation, Ramsar Sites.

GS3 (Science & Technology): Impact cratering, astrobiology, space science.

Key Prelims facts:

• Location: Buldhana district, Maharashtra
• Formation: Meteorite impact ~52,000 years ago
• Diameter: ~1.8 km
• Depth: ~150 m (current)
• Unique: Formed in basaltic rock (rare globally)
• Water: Both saline AND alkaline (pH ~10.5)
• Endorheic: No surface outflow
• 2020 pink colour change: Due to halophile bacteria + algal bloom
• Ramsar Site status: November 2020
• Wildlife Sanctuary (Maharashtra)
• National Geological Monument (GSI)
• Ancient temples: Chalukya period (10-12 centuries)
• Scientific significance: Analog for Mars, Moon research
• Host organisms: Halophiles, alkaliphiles, cyanobacteria
• Nearest airport: Aurangabad
• Bird species recorded: 160+
• No major surface inlet; fed by groundwater