The possibility of life on Mars is a subject of huge interest in astrobiology due to its proximity and similarities to Earth. To date, little proof has been found of past or present life on Mars. Cumulative evidence suggests that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms.
Life on Mars would not necessarily be indicative of a separate evolutionary lineage. The panspermia hypothesis proposes that life may have spread from Earth to Mars, or vice versa.
If life does exist on Mars, it is likely to be small and simple, since the surface of Mars is barren, and no large multicellular life has been seen so far by any of the Mars rovers. The meteorite fragment Allan Hills 84001 was examined in 1996 and was reported to have structures resembling microscopic fossils of bacteria. Wikipedia notes, "scientific consensus is that 'morphology alone cannot be used unambiguously as a tool for primitive life detection.' Interpretation of morphology is notoriously subjective, and its use alone has led to numerous errors of interpretation."
Will we find life on Mars by 2050?
This question resolves positively in the event that prominent, highly respected scientific organizations announce that humans have discovered unambiguous evidence of current or past life on Mars, independent of life that was carried from Earth to Mars via human-designed missions. If by 2050, this has not happened, the question resolves negatively.