Science fiction is filled with examples of weird and wonderful lifeforms from other planets. In particular, the idea of Martians dates back at least as far as 1897, when HG Well's The War of the Worlds was first published. Alongside this interest in fictional aliens, the search for actual Martian life will take its next step this summer - between 30 July and 15 August - when NASA plans to launch its next mission to Mars, the Rover Perseverance.1
Looking for life on Mars is obviously challenging. You can't take a full laboratory to Mars, and all the instruments you do send have to be light enough that they can leave Earth and make it to Mars, and they have to work in the dusty Martian atmosphere. US 10,337,996 B2 describes a Lidar instrument which can overcome these difficulties. The instrument includes two ultraviolet lasers (at 266 nm and 355 nm) and an infrared laser (at 905 nm). Instead of being hindered by the dusty atmosphere, these lasers actually use the dust, firing laser pulses which cause the dust to fluoresce. This fluorescence is measured, and the instrument can detect bio-signatures or bio-indicators in the fluorescence. As well as looking for life, the instrument also measures the size of the dust particles, which is important for understanding the Martian environment. All this is achieved using approximately 1W of power - which is ideal when the nearest spare batteries are millions of miles away!
US 2019/0219510 A1 describes another technique for measuring Martian samples, this time using Raman spectroscopy. Raman spectroscopy is a well-known technique which uses laser light to illuminate a sample. Most of the laser light is scattered away at the same wavelength, but a small amount of the light is scattered at a higher or lower wavelength, and these small changes in wavelength can be used to identify molecules and study chemical bonding in the sample. This is often done in the dark, so that background light doesn't overwhelm the relatively weak Raman scattering. However, the Raman instrument in US 2019/0219510 A1 can use a pulsed laser to illuminated the sample, and the detector can isolate the Raman scattering from any background light by looking for signals which have the same frequency as the laser pulses. This means that samples don't have to be measured in the dark, which is a big advantage when the samples cannot easily be shielded from sunlight.
As well as looking for life on Mars, NASA are also testing technologies which will be needed for humans to one day visit Mars. Obviously, one of the most basic human requirements is breathable air, but the Martian atmosphere is mostly carbon dioxide.2 It would be difficult to take enough oxygen from Earth to Mars to cover all human needs, so instead, NASA are testing a method for converting the Martian atmosphere into breathable oxygen. US 9,776,130 B1 describes an apparatus which can be used for this. The apparatus has a stack of electrochemical cells. A voltage is applied across each cell, and carbon dioxide from the atmosphere is separated into carbon monoxide and oxygen ions at the cathode of each cell. The oxygen ions move through the electrolyte of the cell to the anode, where electrons are removed from the ions and oxygen gas is formed. The oxygen gas moves up the stack of electrochemical cells, resulting in pressurised oxygen gas. As well as being used to made breathable oxygen, this technology could also be used to make the oxygen which would be needed to burn fuel in a rocket for bringing humans back to Earth.
Searching for signs of life and testing technologies which will be needed for humans on Mars are just two of the goals of the Mars 2020 mission. The other two goals are to characterise the climate of Mars, and to characterise the geology of Mars. To help with these goals, Perseverance will also monitor the weather and dust in the Martian atmosphere, and collect core rock and "soil" samples and store them on the Martian surface to be collected by a future Mars mission, and for a possible return to Earth. Once Perseverance lands on Mars in February 2021, it will hopefully produce a lot of interesting data which can teach us more about the Red Planet, and maybe even find our first evidence of a real Martian.
Originally published 9th July 2020.
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