14 | NewScientist | 10 May 2014

This week

Jacob Aron

IN THE hunt for life on Mars, it’s time to pull out the heavy artillery. A non-profit group has proposed a mission that involves showering Mars with bunker-busting missiles that would penetrate deep into the ground but deliver probes, not warheads.

On Mars, preserved traces of microbes could lurk in deep subsurface ice, where they would be shielded from harsh cosmic radiation. NASA’s Curiosity rover has a drill, but it only penetrates a few centimetres. “Curiosity doesn’t go very deep – it is literally scratching the surface,” says Chris Carberry, executive director of the non-profit group Explore Mars, based in Beverly, Massachusetts.

Future missions will go deeper but will have limited capabilities. NASA’s InSight lander mission, set for 2016, features a “mole” designed to dig down 5 metres, but it won’t be searching for life. The European Space Agency’s ExoMars rover, due to launch in 2018, will drill down 2 metres in search of traces of life, but it can only explore a single Martian region.

That’s why Explore Mars last

week appealed for funds for a project called Exolance, which would scatter small, lightweight projectiles across the Red Planet. Each missile would carry scientific instruments and would keep in radio contact with Earth.

The team includes Gil Levin,

who led an experiment on NASA’s 1976 Viking mission that he claims saw evidence of life. NASA maintains that a second on-board experiment ruled out the result. Levin thinks Exolance could both confirm the Viking finding and run versions of the test to see if life emerged independently on Mars.

But first, Explore Mars will need to show that its hardware is robust enough. NASA tried a similar approach in 1999 with its Deep Space 2 mission. Two small probes smashed into Mars

as planned but then failed to established radio contact. “Penetrators result in huge shocks,” says ExoMars project scientist Jorge Vago. “Not many instruments can take this.”

The team also needs to find a ride, as they plan to keep costs low by piggybacking on a mission already headed into space. “It will be tough getting the technology on board a spacecraft headed to Mars,” says Alan Smith at University College London. “Still, it demonstrates that penetrators are being seen more and more as credible platforms for planetary exploration.”

Smith is part of a team developing penetrators for a potential mission to Jupiter’s moon Europa, which is thought to have a subsurface ocean that could host life. Last year they fired dummy probes at targets made of sand and ice and showed that the probes could survive such impacts.

The Exolance team will perform similar tests, and ultimately hopes to release many missiles at once to boost their chances of success. The team believes this approach will be faster and cheaper than sending more landers. “It is not likely we will be able to do an InSight mission again for many years,” says Carberry. “We’re proposing something that would be less expensive – and we might be able to do it much sooner.” n

Fire missiles at Mars to find life

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“X-rays clearly showed the liquid metal injected into a frog leg, letting the team remove it with a syringe”

–Send in the crust-busters–

HASTA la vista, nerve damage. Experiments with frog nerves show that a Terminator-style liquid metal could one day be used to help severed nerves heal.

The peripheral nervous system carries electrical signals from the brain to the rest of the body. As peripheral nerves aren’t protected by the spine or skull they are

Liquid metal may help heal severed nerves

more vulnerable to injuries.Severed nerves can reconnect if

treated quickly enough after an injury, but grow at a rate of just 1 millimetre per day. And if the nerves don’t pass signals to muscles during the healing process, the muscles can atrophy and may never fully recover.

Jing Liu at Tsinghua University in Beijing, China, and his colleagues wondered if liquid metal could help signals pass through a graft while a damaged nerve healed. They used an alloy of gallium, indium and selenium, which is a good electrical conductor. The alloy is liquid at room temperature

so it can be removed with a syringe when no longer needed.

The team tested the alloy on the sciatic nerves of 10 bullfrogs. After removing the nerve, they cut it and reconnected the ends with tubes containing either the liquid metal or Ringer’s solution, a mix of salts that permits some electrical flow.

The nerves reconnected with liquid metal conducted electrical signals

about as well as a healthy nerve, and several orders of magnitude better than nerves reconnected with Ringer’s solution. The team also injected some of the metal alloy into a severed frog’s leg. They were able to easily find the fluid in X-rays and remove it with a syringe (arxiv.org/abs/1404.5931).

Liu cautions that this study is a starting point, and he intends to do more animal tests soon. “Before use in clinics, tremendous evaluations about the safety of the material are needed,” he says. “This is a brand new trial in its initial stage.” Lisa Grossman n

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