Towering blades of ice could get in the way of our search for alien life, scientists have warned.

Jupiter's moon Europa is often held up as one of the most promising places to discover extraterrestrials. It is relatively near and has huge seas of liquid water under its surface, which could provide a home to those aliens.

Scientists hope to eventually land a spacecraft on that icy crust and drill down beneath it to see whatever is lurking in the oceans below.

But on that same alien surface are vast shards and daggers of snow that could destroy any craft that attempted to land there, scientists have warn. Reaching almost 15 metres tall, the blades of sharp ice could be a fatal barrier to any attempt to meet that extra-terrestrial life.

Any potential landing mission would have to navigate those "penitentes" before it could drop onto the surface.

The spikes are formed through a process known as sublimation. That turns ice into water vapour without melting into a liquid between the two, and leaves behind those blade-like formations that point right up into the sun.

Penitentes do grow down on Earth. But here they are restricted to extreme areas such as the Andes and grow between one and five metres tall.

Europa however is much more suited to growing the huge blades because its surface is dominated by ice, it has the right thermal conditions for that sublimation to occur, and the sun always shines at the same angle towards the surface.

"The unique conditions of Europa present both exciting exploratory possibilities and potentially treacherous danger," said lead author of the research Dr Daniel Hobley, from Cardiff University's School of Earth and Ocean Sciences.