WASHINGTON, Oct. 12 (Xinhua) -- U.S. President Barack Obama said confidently on Tuesday that the United States aims to send humans to the planet Mars by the 2030s and return them "safely to Earth".

"We have set a clear goal vital to the next chapter of America's story in space: sending humans to Mars by the 2030s and returning them safely to Earth, with the ultimate ambition to one day remain there for an extended time," he stated in an opinion article written for CNN.

"They've gone to space not just to visit, but to stay -- and in doing so, to make our lives better here on Earth," he added.

However, such optimism seemed to be challenged by a new study, which indicates that astronauts traveling to Mars might be at risk of long-term brain damage and even dementia due to galactic cosmic ray exposure.

To explore a phenomenon called "space brain," researchers from the University of California, Irvine (UCI) exposed rodents to highly energetic charged particles, which are much like those found in the galactic cosmic rays that will bombard astronauts during extended spaceflights, according to the study published in the journal Scientific Reports.

Six months after exposure, the researchers found significant levels of brain inflammation and damage to neurons, said Charles Limoli, professor of radiation oncology in UCI's School of Medicine.

Imaging revealed that the brain's neural network was impaired through the reduction of dendrites and spines on these neurons, disrupting the transmission of signals among brain cells.

These deficiencies were parallel to poor performance on behavioral tasks designed to test learning and memory.

"This is not positive news for astronauts deployed on a two-to-three-year round trip to Mars," Limoli said.

"The space environment poses unique hazards to astronauts. Exposure to these particles can lead to a range of potential central nervous system complications that can occur during and persist long after actual space travel -- such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making. Many of these adverse consequences to cognition may continue and progress throughout life," he added.