麻豆传媒

Earth鈥檚 upper atmosphere has strange dense layers of ions that are constantly appearing and disappearing and which can hamper radio communication. Now, the same thing has now been found on Mars, offering a new chance to crack understand this poorly studied phenomenon.

The ionosphere is the layer of the atmosphere about 60 to 1000 kilometres up that is full of charged particles. When those particles are temporarily blown into clumps by the wind, they form what researchers call sporadic E layers in the lower reaches of the ionosphere.

鈥淭hey act like a mirror in the sky, and radio signals bounce off of them,鈥� says Glyn Collinson at NASA鈥檚 Goddard Space Flight Center in Maryland. 鈥淲hen you turn on your favourite radio station and it鈥檚 jammed by another station, you have probably been the victim of a sporadic E layer.鈥�

They don鈥檛 just interfere with commercial radio stations, though 鈥� they can also block radar signals that are used to detect aircraft and ballistic missiles, he says.

E layers are difficult to study on Earth, because they appear and disappear unpredictably and they are at an altitude that is too high for aircraft to reach and too low for satellite orbits. But Collinson and his colleagues have spotted them in the Martian atmosphere for the first time, where they might be far easier to study.

The team found signs of 34 E layers in data from NASA鈥檚 Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The layers form higher in the Martian atmosphere, so MAVEN is flying right through them and they are probably too high to interfere with any future radio communications on the ground, Collinson says.

MAVEN also found 鈥渞ifts鈥� in the planet鈥檚 atmosphere 鈥� areas with abnormally few charged particles that are the opposite of E layers and have never been spotted on Earth. The layers and rifts seem to always form at the same spots because of how the charged particles in Mars鈥檚 ionosphere react to its tangled magnetic field. That could make them far easier to predict and study there, which could teach us more about them and help us deal with their effects on radio communications here.

鈥淢AVEN has already explored more of these at Mars than we have ever explored on Earth,鈥� says Collinson. 鈥淚t鈥檚 giving us a place where we can finally study this thing that鈥檚 happening right above us all the time that you wouldn鈥檛 know about unless your radio starts speaking Portuguese.鈥�