When Mars quakes, a UK-built instrument will listen

23 November 2018

Mars Insight infographic

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(Credit: UKRI (InSight images: NASA))

NASA’s Mars Insight lander has successfully touched down on the surface Mars in a mission study the heart of the Red Planet and be the first to measure ‘Marsquakes’. One of its key instruments has been built in the UK with the assistance of STFC RAL Space.

On November 26, a spacecraft made its descent to the Martian surface – onboard is a highly sensitive instrument designed and built right here in the UK.

The craft, called InSight (Interior Exploration using Seismic Investigations), used its heat shield, parachutes and retrorockets to slow itself from a stomach-churning 12,300mph and make the descent to the surface. This perilous journey is known to mission controllers as the ‘seven minutes of terror’ for good reason because, historically, some 60 per cent of landings have ended in failure (a phenomenon that the more superstitious refer to as ‘the curse of Mars’).

Safely on the surface, the lander phoned home to let everyone know it arrived safe and sound and that is was ready to begin listening to the planet’s seismic heartbeat.

Unlike other Mars missions, which have focused on exploring surface features, InSight will be the first to dedicate its time to exploring the inner-workings of the planet – allowing scientists to get their first look deep beneath the surface of Mars. The mission will answer key questions about the planet’s structure that will help us to understand how planets formed in the early Solar System. It will do this using the science of seismology.

Although Mars is far less seismically active than the Earth, it is thought to experience the Martian equivalent of earthquakes – known, logically enough, as Marsquakes. When rocks crack or shift during such a quake, they give off seismic waves that travel through the planet. These waves travel at different speeds depending on the material they are travelling through so, by listening to these quakes and measuring their size, frequency and speed, scientists can build up a picture of the material they are passing through.

Each time a quake happens, it will give scientists a ‘snapshot’ of the Martian interior that, over time, and the several hundred quakes InSight is expected to witness, will build up to create a detailed picture. It was this technique that allowed geologists to figure out the internal structure of the Earth and the Moon – Apollo astronauts deployed seismometers on the lunar surface and set off explosions to create seismic waves. InSight will be the first attempt to conduct seismology on Mars since the Viking landers attempted and failed do so in the 1970’s.

Unlike the Viking landers, which had their instruments wobbling around on top of the craft, Insight is armed with a series of extremely sensitive seismometers that will be placed firmly on the Martian surface.

left-hand quote markI’m thrilled that the landing was so successful – it’s a real testament to the brilliant work that the teams across the US and Europe have put into this project. Now we get to explore the inside of Mars!right-hand quote mark

Rain Irshad – Autonomous Systems Group Leader, RAL Space

The mission’s primary seismometer is a large dome-shaped instrument called SEIS (Seismic Experiment for Interior Structure) that uses three extremely sensitive pendulums to detect the tiniest movements of the Martian surface. SEIS is supplemented, and backed up, by a UK-built instrument called SEIS-SP (short period seismometer), which is the result of a collaboration between Imperial College London and Oxford University supported by STFC RAL Space. The UK Space Agency invested £4 million into the instrument. SEIS-SP will act as InSight’s ‘second pair of ears’.

While SEIS is a miracle of sensitivity, SEIS-SP is a miracle of miniaturisation. Unlike SEIS’s pendulums that weigh in at 190g each, SEIS-SP sensors barely tip the scales at just 1g and yet are capable of detecting vibrations in three spatial dimensions (up-down, left-right, back-forth). Despite their sensitivity, they are tough enough to survive the trauma of a rocket launch and the violence of a Martian landing.

InSight’s seismometers are so sensitive they will be able to detect seismic shifts smaller the width of a hydrogen atom, which, in case you were wondering, is very small indeed. This sensitivity will allow the craft to detect the tiny seismic signals generated when meteors impact the Martian surface – data that will be used to supplement that gathered from Marsquakes.

InSight will also use radio signals to investigate whether Mars still has a molten core and is armed with a self-burrowing probe that can dig five metres beneath the surface to take the planet’s temperature and investigate how heat moves though the Martian interior. Combining all this data, gathered over the mission’s two-year duration, will give us the most complete picture of Mars yet and help answer one of the biggest questions in planetary science: how are planets born?

View full infographic (PDF, 940 KB)

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Last updated: 07 December 2018

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