The Mars Odyssey Orbiter has been on the Martian orbit since its launch in 2001. What Odyssey discovered were vast quantities of hydrogen thought to be stored in the water ice in large deposits.
ESA or European Space Agency, to be more exact, launched in 2003 the craft called Mars Express. It contained the Beagle 2 lander and the Orbiter. However, Beagle 2 did not land on the Martian surface and in February 2004 it was declared lost. The team of Planetary Fourier Spectrometer announced at the beginning of 2004 that methane had been detected in the atmosphere of the planet Mars, while two years later, in 2006, ESA announced they had discovered aurorae on the planet Mars.
Spirit and Opportunity are two rovers launched in 2003 by NASA in the Mars Exploration Program. Both of them successfully landed on Mars in January 2004 and they have been operating important scientific research ever since, even with extensions of the initial mission. A very important piece of information that they delivered was the evidence of liquid water existence on the Martian surface. Due to some windstorms or dust devils, the solar panels on both rovers were cleaned, so the lifespan of Spirit and Opportunity increased.
NASA launched another Mars mission in 2005, called the Mars Reconnaissance Orbiter. It entered the Martian orbit in 2006 and conducted a science survey for the following two years. Among its objectives were to find possible landing sites for future spacecrafts and to characterize the Martian weather and terrain. Its telecommunication system is more developed than all the ones of all the previous missions. In 2008 Mars Reconnaissance Orbiter provided a first image of several active avalanches somewhere close to the Martian North Pole.