Search the World Wide Web for information about the Mars Express orbiter and the Spirit and Opportunity rovers. What discoveries have these missions made about water on Mars? Have they found any evidence that liquid water has existed on Mars in the recent past? Describe the evidence, if any.

Launched by the European Space Agency (ESA) in June 2003, the Mars Express Orbiter was Europe's first mission destined for another planet. Its primary objective has been to search for evidence of water and explore the Martian atmosphere and geology. By analyzing the mineral composition of the Martian surface, Mars Express has discovered signs of water-rich minerals and ancient water-eroded valleys.

One of the significant breakthroughs was the detection of hydrated minerals, which indicates that water was present during their formation. Moreover, the orbiter's OMEGA spectrometer has found traces of sulphates and silicates, which also suggest the past presence of water. Importantly, radar data from the MARSIS instrument hinted at subsurface reservoirs of water ice, thus providing strong evidence of water's historical presence beneath the surface.

The twin rovers, Spirit and Opportunity, touched down on Mars in January 2004, starting their mission to uncover the planet's past water history. Their exploration focused on studying rocks and soils for clues about past wet conditions that may have been conducive to life.

During their missions, both rovers found a variety of rocks and soil that provided evidence of the historical presence of water. Opportunity made a landmark discovery in the form of hematite, a mineral that typically forms in water, at its landing site, Meridiani Planum. Moreover, Opportunity uncovered cross-bedded rock formations indicating the past flow of water, and also spherical formations known as 'blueberries' formed in aqueous conditions. Spirit, on the other hand, discovered silica-rich soil patches that scientists believe formed in the presence of hot springs or steam vents, suggesting watery environments in the past.

The quest to find evidence of liquid water on Mars is a pivotal aspect of understanding the planet's potential to harbor life. Various missions, including the Mars Express Orbiter and the rovers, have contributed to the belief that Mars once had significant amounts of surface water.

Recent studies have increased the anticipation of finding liquid water, as they suggest the presence of a subsurface lake beneath Mars' south polar ice cap and seasonal flows of briny water on the planet's slopes. These findings are compelling as the presence of liquid water, even in brine or ice form, may provide the necessary conditions for life as we know it to exist, or to have existed, on the Red Planet.

Mars has been a focal point for space exploration missions due to its potential for past or present life, as well as its similarity to Earth in various geological aspects. The quest to understand the Red Planet has led to numerous missions by space agencies worldwide.

Each mission aims to uncover a different piece of the Martian puzzle. Rovers such as Curiosity, Spirit, and Opportunity probe the Martian surface, drilling into rocks and analyzing soil, while orbiters like the Mars Reconnaissance Orbiter and Mars Express scan the planet from above. These missions have been invaluable in enhancing our understanding of Mars' atmosphere, climate, geology, and the quintessential question of water's presence. Together, they pave the way for future missions that may one day see humans set foot on Martian soil.