What are terrestrial analogue sites? Discuss their significance for India's planetary exploration programme, citing recent Indian examples.

Terrestrial analogue sites are places on Earth whose minerals, landforms or climate resemble those of another planetary body. Orbital data alone cannot fully characterise Martian minerals [1]. These sites therefore let scientists check mission data against ground samples, test instruments and train crews before costly missions.

Types of analogue sites

• Mineralogical analogues have the same mineral chemistry and formation processes as planetary rocks.
• Habitat/operational analogues reproduce physical extremes so that crews, habitats and equipment can be tested.

Recent Indian examples

• Neyveli (Tamil Nadu): University of Kerala geologists used a DST-FIST-funded laser Raman spectrometer to identify melanterite. It is a hydrous sulphate that points to short-lived wet, acidic, oxidising conditions [1].
• Tiruchirappalli Badlands and Atacama (Chile): The team found gypsum at both sites. It records past water activity and can preserve biosignatures. The findings were published in JGR: Planets [1].
• HOPE, Tso Kar (Ladakh): ISRO opened this habitat analogue in July 2025. The site was chosen for its high UV, low air pressure, extreme cold and saline permafrost, which resemble early Mars [3].

Significance for India's planetary programme

• Scientific: Raman "spectral fingerprints" of Indian sulphates give reference data for reading Mars's water history [1].
• Mission planning: Minerals that record water and preserve biosignatures can help choose landing and sampling sites [1].
• Human spaceflight: HOPE produces crew health and performance data for future Indian human exploration [3].
• Capacity building: DST-FIST funding let a state university do frontier science. FIST facilities must be listed on the I-STEM portal so other institutions can use them [2].

Limitations

• The Tamil Nadu sites are warm and at Earth's air pressure. They match how the minerals form, not the conditions on the Martian surface [1].
• Biosignatures in Earth's gypsum are expected, so they cannot prove life on Mars.
• India's only Mars mission so far, Mangalyaan (2013), was an orbiter [4]. Ground-sample data will pay off fully only once India sends its own lander.

Together, Tamil Nadu's mineral sites and Ladakh's habitat station give India two analogue types that complement each other. DST and ISRO should build a public Raman reference library of Indian minerals and open the instruments to other researchers through I-STEM. They should also field-test portable spectrometers at these sites before a surface mission, so that local geology becomes a foundation for Atmanirbhar (self-reliant) planetary exploration.