Five sentences related to a topic are given below. Four of them can be put together to form a meaningful and coherent short paragraph. Identify the odd one out. Choose its number as your answer and key it in.

1. The water that made up ancient lakes and perhaps an ocean was lost.

2. Particles from the Sun collided with molecules in the atmosphere, knocking them into space or giving them an electric charge that caused them to be swept away by the solar wind.

3. Most of the planet's remaining water is now frozen or buried, but clues over the past decade suggested that some liquid water, a presumed necessity for life, might survive in underground aquifers.

4. Data from NASA's MAVEN orbiter show that solar storms stripped away most of Mars's once-thick atmosphere.

5. A recent study reveals how Mars lost much of its early water, while another indicates that some liquid water remains.