The methane mystery

The methane mystery Methane on Mars is really interesting – and really hard to explain.

On Earth, methane signals microbes: they produce it, lots, as they break down organic matter. Although there are other, non-living sources of methane, such as some geological processes, it is generally considered a useful biomarker: i.e. if you find methane, you may have found life. No wonder scientists are all excited to find lots of it.

At least, lots according to the Mars Curiosity Rover. But very little according to the ExoMars Trace Gas Orbiter (TGO) – which is where most of the mystery comes in.

 

Artist's impression of the Curiosity landing on Mars – NASA.

India's MOM seeks answers

In 2010 the Indian Space Research Organisation (ISRO) began a mission to send a spacecraft to orbit Mars – the Mars Orbiter Mission (MOM). Three years later they launched the craft and finally, on 24th September 2014 it reached its destination. The spacecraft’s primary objective is to test and develop the necessary technologies needed for interplanetary space travel - a technology which will allow India to plan future missions through the solar system and beyond. Its secondary objective, though, is scientific research. As the craft orbits the planet it will be collecting data about the planet’s atmosphere and surface.

The journey to Mars, though relatively short compared to a journey to other planets, is a complicated one; out of the 23 missions which have been launched to orbit Mars, only 10 have been fully successful. For India, this maiden voyage means the chance to explore the red planet whilst also developing their technological know-how. The whole mission has cost ISRO about $70 million - making it the cheapest vessel to enter Mars’ orbit since exploration of the planet began! For comparison, NASA had to pay a similar amount per seat to fly their own astronauts to the International Space Station in a Russian spacecraft. This is an incredible feat for technology and may lead to reduced costs for future missions to Mars.

An artist's impression of the Mars Orbiter Mission spacecraft orbiting Mars. The basic structure was based closely on ISRO’s first mission - Chandrayaan-1. Image credit: Nesnad, via Wikimedia Commons. (CC-BY-SA-3.0)

Mars is the outermost of the four rocky planets in our Solar System, and is also Earth’s neighbour. Despite having similar rocky compositions these two planets couldn’t be more different. The oceans, flora and fauna which are so prevalent on Earth are completely absent on Mars, and yet the two planets’ orbits are separated by a mere 54.6 million kilometres – a galactic stone’s throw away. Astronomers and planetary scientists have been studying the planet for a while now, and yet there is still so much we cannot decipher about the planet and its history.

Celebrating 10 years of Mars Express

At the beginning of June, the European Space Agency (ESA) celebrated the 10 year anniversary of the Mars Express mission. The spacecraft, launched in 2003, has had ten successful years of operation and has resulted in the publication of over 600 scientific papers. To help mark this occasion, our intern Cait interviewed Olivier Witasse, the mission's Project Scientist, about some of the key discoveries the spacecraft has made and what the future of the mission looks like.

Mars Express has had ten very successful years in orbit around Mars. Image credit: ESA

One of the key themes of space exploration is the search for life. We base our search for past or current life on the presence of liquid water – it's vital for life like ours so it's one of the first conditions we look for. Direct evidence of past water on Mars is one of the key findings and surprises of the Mars Express mission:

"...from what we have been discussing with the scientists over the last year, there is one result which I think is really on top of the others - the discovery of the so called hydrated minerals."

Before the discovery of hydrated minerals, scientists at ESA were expecting to find carbonates on what may have once been a sea bed. Finding carbonates would imply that there were once large oceans on Mars. Carbonates can form in one of two ways - a purely chemical reaction where carbon dioxide in the atmosphere is dissolved by the surface water of an ocean or as a result of the shells of past marine creatures. If the oceans were absorbing atmospheric carbon dioxide then further reactions with minerals (i.e. magnesium, calcium) in the ocean would produce carbonates which would settle onto the ocean floor. The atmosphere on Mars is mostly carbon dioxide, so if there were once oceans on Mars we would expect the formation of these carbonates. The shells of some marine animals also contain carbonates, so when the creatures die, their shells sink to the bottom of the ocean to form carbonate deposits with the possible preservation of fossils. These carbonates would remain even when the ocean faded away.