Discuss how Mars missions have changed the understanding of extraterrestrial water. What lessons does India's Mars Orbiter Mission offer for low-cost planetary exploration?

Fifty years ago, Viking scientists reported that the Martian north polar cap was largely water ice rather than frozen carbon dioxide [1]. Successive missions have since moved the question from whether water exists beyond Earth to where, how much, and how usable it is.

From discovery to measurement

• Viking (1976): orbiter observations confirmed the northern residual cap gives off water vapour in summer as ice sublimes — ending the assumption of a purely CO₂ cap [2].
• Quantification: radar sounding by MARSIS on ESA's Mars Express measured the north polar deposits at about 1.8 km thick and nearly pure water ice, replacing speculation with a bounded figure [3].
• From poles to landing zones: NASA's SWIM project maps buried ice in the upper ~1 m from the equator to 60°N — latitudes cold enough to hold ice yet warm enough to land on [4].
• Method lesson: one remote-sensing signal usually has more than one explanation; confirmation requires a second, independent instrument.

Lessons from the Mars Orbiter Mission

• Frugal engineering: MOM flew on PSLV-C25 (5 November 2013) into a highly elliptical orbit, trading close repeat passes for a cheaper launcher and simpler insertion [5].
• Payload discipline: five light instruments — colour camera, methane sensor, thermal infrared spectrometer, exospheric analyser and Lyman-alpha photometer measuring deuterium/hydrogen, an index of water lost to space [5].
• Longevity: designed for six months, it operated for over seven years, maximising science per rupee [5].
• Strategic value: PIB records MOM as the world's most economical interplanetary mission, opening cost-effective access to deep space [5][6].
• Limitation: lacking a subsurface radar, MOM could not address buried ice — a gap for Mangalyaan-2.

Mars exploration shows that water questions are settled incrementally, instrument by instrument. India's contribution lies in proving that credible planetary science need not be expensive. Carrying this frugality into a radar-equipped successor, alongside international data-sharing, would let India move from participation to leadership in the search for extraterrestrial water.