Evidence of life on Mars

Water has been a topic of fascination for humans since the beginning of time. It is an essential element for life, and its presence or absence has been a determining factor for the habitability of a planet. For many years, scientists have been searching for water on other planets, and one planet that has captured their attention is Mars. Mars, often referred to as the "Red Planet," is the fourth planet from the sun and the second-smallest planet in the solar system. It is a cold and harsh planet, with a thin atmosphere and a barren landscape. However, recent discoveries have shown that water may have once flowed on its surface and could still exist there today.

The search for water on Mars dates back to the 19th century when Italian astronomer Giovanni Schiaparelli observed dark, linear features on the planet's surface, which he called "canali," meaning channels in Italian. These features sparked the imagination of many, and some even believed they were evidence of an advanced civilization on Mars. However, further observations and studies revealed that these features were, in fact, just an optical illusion caused by the contrast of light and dark regions on the planet.

It wasn't until the 1960s that spacecraft sent to Mars started providing more concrete evidence of water on the planet. In 1965, the Mariner 4 spacecraft took photos of Mars' surface, showing evidence of ancient riverbeds and canyons, indicating that water may have once flowed on the planet's surface. This discovery fueled the idea that Mars may have once been a warmer and wetter planet, similar to Earth, and could have potentially supported life.

In 1971, the Mariner 9 spacecraft provided further evidence of water on Mars by capturing images of dried-up riverbeds, floodplains, and ancient lakebeds. These features were similar to those found on Earth, further supporting the theory that Mars may have once had a more hospitable environment. However, the question still remained – where did all the water go?

Through subsequent missions, scientists were able to determine that Mars lost most of its water due to a combination of factors. The planet's low gravity and lack of a protective magnetic field allowed solar winds to strip away its atmosphere, including its water vapor. Additionally, the planet's cold temperatures caused the remaining water to freeze and become trapped in its polar ice caps.

Despite these challenges, scientists have continued to search for water on Mars, and in 2008, the Phoenix lander confirmed the presence of water ice near the planet's north pole. The lander also detected water vapor in the planet's atmosphere, further supporting the theory that Mars still has water in some form.

In 2011, the Mars Reconnaissance Orbiter (MRO) discovered dark streaks on the planet's surface known as "recurring slope lineae" (RSL). These features were found to change with the seasons and were believed to be caused by the flow of water, possibly from underground ice melting and seeping out onto the surface. This discovery raised the possibility that liquid water may still exist on Mars, albeit in small amounts and for short periods of time.

In 2015, NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft provided further evidence of the presence of liquid water on Mars. The spacecraft detected large amounts of deuterium, a heavier form of hydrogen, in the planet's atmosphere. This finding suggested that Mars may have lost a significant amount of its water to space, but some of it may have been trapped underground or in the polar ice caps.

In 2018, the MRO also detected a lake of liquid water under the planet's south polar ice cap, providing the strongest evidence yet of present-day liquid water on Mars. The lake, estimated to be about 20 kilometers wide and a meter deep, was found using radar data and was confirmed by a separate study using measurements of the planet's gravity.

The discovery of liquid water on Mars has significant implications for the planet's potential to support life. It opens up the possibility of microbial life existing in the underground lakes and aquifers, and it also provides a potential source of water for future human missions to the planet.

In 2019, NASA's InSight lander also detected water vapor in the planet's atmosphere, further solidifying the evidence of water on Mars. The lander is also equipped with a probe that can measure subsurface temperatures, providing valuable data on the distribution of heat and potential underground water sources.

The search for water on Mars is ongoing, and future missions are planned to explore the planet's surface and subsurface in more detail. The Perseverance rover, which landed on the planet in February 2021, is equipped with instruments specifically designed to search for signs of past microbial life and to study the planet's geology, including its water history.

In conclusion, the discovery of water on Mars has come a long way since the 19th century, and with each new mission and discovery, we are getting closer to understanding the planet's history and potential for life. While the planet may never be able to support human life as we know it, the presence of water on Mars is a crucial step in our understanding of the universe and our place in it.