Methane on Mars

I was very excited to read about the discovery published last week by NASA’s Curiosity rover of the seasonal variation in the amount of methane in Mars’ atmosphere. Curiosity found that the average methane concentration varied from 0.24 parts per billion (ppb) in the northern hemisphere winter to around 0.65 ppb in the summer.

This was widely reported in the world’s media e.g.the New York Times.The interesting fact is that, on Mars, methane should have a very short lifetime because it is destroyed by ultraviolet light from the Sun. The presence of any methane in Mars’ atmosphere means that there must be some process, as yet unknown, continually producing it.  On Earth nearly all methane is biological in origin and is generated by microorganisms as a waste product. The seasonal variation in methane in Mars’s atmosphere is certainly consistent with life, but there may be other non-biological processes making this methane.

A joint mission between the European Space Agency (ESA) and the Russian space agency, called the TGO has just started scientific operations and may shed more light on the origin of this methane. I’ve therefore attached an updated version of my earlier post about this spacecraft.

————–

Two years ago on 14 March 2016 the ExoMars Trace Gas Orbiter (TGO) spacecraft was launched from Baikonur, Kazakhstan on a journey to Mars. The purpose of its mission is to study how the distribution of the gas methane varies with location on the planet’s surface and over the course of time.

Trace Gas orbiter

Image from ESA

What is the significance of methane on Mars?

Compared to the Earth, Mars has a very thin atmosphere. Its surface pressure is only 0.6% of that of the Earth. The atmosphere mainly consists of carbon dioxide. However, it also contains a small amount of methane, around 0.5 parts per billion. This is a puzzle to scientists because the ultraviolet light from the Sun should break up any methane within 600 years, and Mars is 4.5 billions old. Therefore there must be some process occurring which is constantly replenishing the methane.

Mars NASA

Mars- Image from NASA

There are various possibilities for the origin of this methane. One is that it is released by geological processes such as volcanoes or a chemical process occurring within rocks called serpentinisation. This is not as exciting as it sounds (no snakes, I’m afraid) – it is simply a slow chemical reaction between olivine (a mineral found on Mars) carbon dioxide and water which can produce methane.  Another is that there is a large reservoir of methane locked away in the ice below the Martian surface and as the temperature varies some of the ice may melt, thus releasing the methane into the atmosphere.

A fascinating possibility is that the methane is created by microorganisms below the planet’s surface.  On Earth more than 90% of methane in the atmosphere is produced by living organisms (ESA 2014). There are over 50 species of microorganisms known as methanogens that live off organic matter and produce methane as a waste product.  These microorganisms are found not only in wetlands (producing what is known as marsh gas) and in the soil but also in the guts of many animals such as cows and humans.  At the risk of sounding somewhat vulgar, the methane gas escapes from both cattle and ourselves in the form of flatulence.

methanogen

Methanogens

What will the TGO measure?

The TGO will measure how the methane content of Mars’s atmosphere varies with space and time. It will also be able to measure the concentration of other gases such as sulphur dioxide (which on Earth is normally associated with volcanic activity) and organic compounds such as ethane, methanol and formaldehyde (which on Earth are produced by living organisms).  Although the TGO won’t be able to say for definite what the sources of the methane found on Mars are, if the concentration of methane were found to vary with the seasons and also if methane were found in conjunction with other organic chemicals it would point towards a biological origin.

How long with the mission be?

The TGO is a joint mission between the European Space Agency (ESA) and the Russian Space Agency (Roscosmos).  The mission is described in more detail on the ESA website  (2018).  It arrived at Mars in October 2016 and was initially placed in a high elliptical orbit around the planet. It took until March 2018 to gradually manoeuvre into the intended orbit and, now it is in the correct position, will spend the next five years mapping the methane distribution. This is a low circular orbit only 400 km from the planet’s surface. The orbit is inclined at an angle of 74 degrees to Mars’s equator. This high inclination enables the spacecraft to see most of the planet’s surface.

The high inclination of the TGO’s orbit means that, as the planet rotates, all area of Mars between latitudes -74 degrees South and 74 degrees North will at some stage be directly below the TGO.

Footnote- Schiaparelli

When the TGO arrived at Mars, it it deployed a small lander called Schiaparelli. This was an ‘add on’ to the main mission and was only designed to operate for a week on the Martian surface. Schiaparelli was intended to measure the wind speed and direction, humidity, pressure and surface temperature, and determine the transparency of the atmosphere. Sadly, when Schiaparelli arrived in the upper regions of the Martian atmosphere, a parachute to slow it down failed to open properly and it crashed into the surface at thousands of km/h and will was destroyed by the impact.

References

ESA (2014) The enigma of methane on Mars, Available at:http://exploration.esa.int/mars/46038-methane-on-mars/ (Accessed: 20 March 2016).

ESA (2018) Robotic exploration of Mars, Available at:http://exploration.esa.int/mars/46124-mission-overview/ (Accessed: 12 June 2018)

Enceladus -Could there be life?

Three years ago my first ever post was about Saturn’s moon Enceladus. It is interesting that once again this small moon is in the headlines as a possible place on which there could be life.

https://www.nasa.gov/press-release/nasa-missions-provide-new-insights-into-ocean-worlds-in-our-solar-system

The Science Geek

The Science Geek

Welcome

Hello and welcome to the first post from the Science Geek 01. I intend to write  a weekly blog about various topics of interest, which will cover all aspects of science. The articles will be aimed at the non scientist and won’t require any previous detailed knowledge. I hope you enjoy reading them and please feel free to comment.

My first posts will deal with the subject of life within the solar system, which in astronomical terms is our own backyard.

Life on Mars

Throughout most of the twentieth century many scientists thought that there could be life on Mars. Indeed the famous American astronomer Percival Lowell (1855-1916) claimed to have seen through his telescope  a large network of canals built by an intelligent civilization  and even produced maps of the Martian canal network. These  canals certainly provided great material for science fiction writers but they were probably all due to Lowell’s imagination!

Percival Lowell’s Martian…

View original post 492 more words

The Evening Star-Venus

Anybody who has looked up into the western sky after sunset in the past month will have noticed a brilliant white object – the planet Venus,  sometimes called the Evening Star. It is brighter than any other planet and ten times brighter than the brightest star Sirius, also known as the Dog Star.

evening-star

The “Evening Star” Venus next to the Moon just after sunset – image from NASA

There are three reasons why Venus is so bright. Firstly, it comes closer to the Earth than any other planet.  Secondly, it is relatively large compared to other inner planets, roughly twice the diameter of Mars and three times that of Mercury. Although the giant planets – Jupiter, Saturn Uranus and Neptune – are larger than Venus, they are further away and so appear smaller. Thirdly, the thick clouds which completely cover Venus reflect most of the light back into space. In fact Venus reflects 65% of the sunlight hitting it, more than any other planet. Venus is so bright that it even possible to see it during daylight. If you know exactly where to look it appears as a faint white dot against the bright blue sky

Venus over the next two years

Venus is both closer to Sun and moves faster in its orbit than the Earth and, on average, it takes 584 days for Venus to be in the same place in its orbit as seen from the Earth. The reason for this 584 day cycle is given in the notes at the bottom of this post. Because the orbit of Venus is inside the Earth’s orbit, Venus can never appear too far away from the Sun in the sky.  In general it is only clearly visible for at most a few hours before sunrise or a few hours after sunset (see note 2). The two points where Venus appears furthest away from the Sun are called the greatest elongation points and are marked as A and B in the diagram below.

venus-next-two-years

 

Data from Espinak (2014)

Venus has just passed a greatest elongation point which it reached on 12 January 2017, and it is a brilliant object in the western sky, visible for at least 3 hours after sunset, depending on your latitude.  Over the next few month as it gets closer to the Sun it will be visible for a shorter and shorter time after sunset. On 25 March Venus will pass between the Earth and the Sun. This is known as inferior conjunction, and for a few weeks or so either side of this date Venus will be very difficult to see because it will only be visible in daytime close to the Sun.

Looking the diagram above, you might think that Venus will pass directly in front of the Sun at inferior conjunction. However, this diagram only shows the picture in two dimensions. As shown below, because the orbit of Venus is tilted with respect to the Earth, at inferior conjunction it normally passes above or below the Sun.

venus-orbital-tilt2

Rarely at inferior conjunction Venus will pass directly in front of the Sun. When this occurs it is known as a transit of Venus.

Transit of Venus

A transit of Venus. Venus is the dark dot crossing the Sun’s surface – image from Wikimedia Commons

After inferior conjunction, it will appear to move away from the Sun and will rise and set earlier in the day and will start to become visible in the eastern sky before sunrise. At this point in its orbit Venus is known as the Morning Star. It will reach the other greatest elongation point on 3 June 2017, when it will be visible for least 3 hours before sunrise.

After reaching the greatest elongation, Venus will start to move closer to the Sun again. It will be visible for a shorter and shorter time before sunrise. On 9 January 2018 Venus will be directly behind the Sun. This is called superior conjunction and, for a few weeks or so either side of this date, Venus will be very difficult to see because it will only be visible in daytime and will appear close to the Sun. After superior conjunction Venus will appear in the evening sky after sunset and as it gets further from the Sun it will be visible for longer and longer before the Sun sets

On 17 August 2018 Venus will reach the greatest elongation point it had previously reached on 12 January 2017 and once again it will be visible for at least 3 hours after sunset as a brilliant object in the western sky.

Venus’s phases during the 584 day cycle

As seen from the Earth over the 584 day cycle, Venus goes through a full set of phases in a similar way to the Moon.  However, because Venus appears so small, these are only visible through a telescope.

Venus Phases

At inferior conjunction, point A in the diagram above, when Venus is between the Earth and the Sun, the sunlit part of Venus faces away from us making the planet almost invisible. The amount of the sunlit part of Venus we can see gets larger or waxes through to a crescent phase (B), to a half Venus (C) at the greatest elongation and then to a full Venus at superior conjunction (D), when the whole sunlit side facing the Earth is illuminated.  It then gets smaller or wanes back to a half Venus (E) at greatest elongation, then to a crescent (F) and then finally back to being almost invisible at inferior conjunction

Galileo’s discovery

The first person to discover the phases of Venus was the Italian astronomer Galileo Galilei (1564-1642).

Galileo_Galilei

Image from Wikimedia Commons

In 1543, just before his death, Nicolas Copernicus (1473-1543) had published the theory of heliocentrism which was completely revolutionary in its day – that the planets orbit the Sun. However, in Gallileo’s time, the teaching of the Catholic church favoured geocentrism, the widely held view that the Earth was the centre of the Universe and the stars, planets, the Sun and the Moon were in orbit around it. Indeed certain verses of the bible could be interpreted as supporting that viewpoint, such as Psalm 104:5  “the Lord set the earth on its foundations; it can never be moved.”

However, the phases of Venus and the way that it appears smaller when it is a full Venus can only be fully explained by Venus orbiting the Sun, not the Earth.  Therefore, Galileo concluded that the geocentric theory was incorrect.   Unfortunately for Galileo, in 1616 the Catholic church declared heliocentrism to be heresy. Heliocentric books were banned and Galileo was ordered to refrain from holding, teaching or defending heliocentric ideas.

Despite this ruling Galileo continued to defend heliocentrism, and in 1633 the Roman Inquisition found him “vehemently suspect of heresy”, sentencing him to indefinite imprisonment. Galileo was kept under house arrest until his death in 1642.

However the facts cannot be disputed. When viewed through a telescope Venus does show changes in size and shape, which can only be satisfactorily explained in a heliocentric model. Eventually, in 1758, the Catholic Church dropped the general prohibition of books advocating heliocentrism.

And finally….

I hope you have you have enjoyed this post. In 2015 and 2016  I published a series of posts on Venus. Some of them are listed below.

Venus a Mysterious world describes Venus in science fiction and compares it these depictions of the planet to reality.

Radio_man

Akatsuki – a second chance describes the mission of the Japanese spacecraft Akatsuki which is currently in orbit around Venus studying its weather. The spacecraft should have gone into orbit in 2010. This didn’t happen but mission control were able to successfully put the spacecraft in hibernation for 5 years before making another successful attempt.

Akatsuki Venus

Terraforming Venus describes how in the future we could alter Venus to make it more Earth-like so that we could live on the planet without needing any special protective equipment.

TerraformedVenus

Notes

(1) The diagrams below illustrate why it takes 584 days for Venus to be in the same position in its orbit in relation to the Earth. Venus and the Earth in their orbits around the Sun are like two runners on a track. The Earth takes 365.256 to do one circuit, whereas Venus, whose orbit is inside the Earth and moves faster around the Sun, only takes 224.701 days to do one circuit.

The point in time when Venus is closest to the Earth and lies between the Earth and the Sun is called inferior conjunction. The time interval between one inferior conjunction and the next is the time it takes for Venus to ‘gain a lap’ in its orbit around the Sun. This is shown in the diagrams below.

Venus 584 day 1

Venus 584 day 2

Venus 584 day 3

Venus 584 day 4

After approximately 580 days Venus and the Earth line up again.

In fact, because the Earth’s and Venus’s speed in their individual orbits isn’t constant but varies slightly, the interval between one inferior conjunction also varies. On average it is 584 days but it actually varies between 580 and 588 days.

 

(2) Strictly speaking, this depends on the latitude of the observer. Venus is visible for much longer at higher latitudes.

References

Espenak, F (2014) 2017 calendar of astronomical events, Available at: http://www.astropixels.com/ephemeris/astrocal/astrocal2017gmt.html (Accessed: 6 January 2017).

 

Schiaparelli on Mars -updated

As most of you will already know, and much to our disappointment, the Schiaparelli probe failed to land successfully on Mars last Wednesday. The plan was that when it entered the Martian atmosphere, the spacecraft would immediately begin to slow down to 1700 km/h as a result of the friction caused by the atmosphere hitting its heat-shield.  When it reached this speed, and was 11 km above the Martian surface, a parachute would open for two minutes to slow it down to 240 km/h. The parachute would then be jettisoned to get it out of the way, allowing thrusters to fire like the brakes on an aeroplane.  The spacecraft would then touch down on the planet’s surface at a gentle 10 km/h.

schiaparelli_landing

Image from ESA

Unfortunately, what appears to have happened is that the parachute only opened for a few seconds and so failed to slow the spacecraft down. The spacecraft will have crashed into the surface at thousands of km/h and will have been destroyed by the impact. It is very disappointing for the European Space Agency(ESA), especially since their only previous attempt to land on Mars (Beagle 2) back in 2003 ended in failure. However It’s not all bad news as Schiaparelli had only a small suite of instruments and was only designed to last for about a week on the Martian surface. The main spacecraft of the mission, the ExoMars Trace Gas Orbitor (TGO), is now successfully in orbit around the planet, and is set to study the way methane is distributed in the Martian atmosphere.

—Original post below

On 14 March 2016 ESA used facilities at  Baikonur in Kazakhstan to launch their long awaited mission to Mars, the not so snappily named ExoMars Trace Gas Orbiter (TGO) and, bolted onto it, a smaller probe called Schiaparelli. Although the much larger TGO will only orbit Mars, next Wednesday, 19 October, Schiaparelli will attempt to land on the surface of of the planet, after its seven month journey.

Assuming all goes well, the spacecraft will land on a flat area called Meridiani Planum, close to the equator. Currently this region on Mars is in its dust storm season. Dust storms occur often on Mars and can be very large, covering an area the size of the US, and may last for many weeks. During a dust storm the dust is so thick that it is not possible to see the Martian surface from Earth or even a spacecraft orbiting the planet. It also blocks much of the sunlight from reaching the planet’s surface. This was an important part of the storyline in “The Martian” where the hero’s car batteries were unable to move due to the lack of solar power, nearly stranding him.

Schiaparelli carries a collection of instruments called DREAMS (Dust characterisation, Risk assessment, and Environment Analyser on the Martian Surface), to study the Martian environment.

The DREAMS instruments will be able to measure the local wind speed and direction, humidity, pressure, atmospheric temperature, the transparency (or how the amount of light which which gets through the atmosphere varies) and atmospheric electric fields which may be caused by dust.  Unlike nearly all other spacecraft, Schiaparelli will have a non- rechargeable battery. The battery will only last for about a week, after which the spacecraft will run out of power and stop functioning. The decision to go for non chargeable battery was made because Schiaparelli is a relatively simple lander, with a small set of instruments and will have completed its mission within the week in which it will be operational. The main part of the mission, however, is a spacecraft which will orbit Mars for at least 6 years, and this is the TGO.

The aim of the TGO is to study how the distribution of the gas methane varies according to its position on the planet’s surface and over the course of time.

Trace Gas orbiter

Image from ESA

What is the significance of methane on Mars?

Compared to the Earth, Mars has a very thin atmosphere. Its surface pressure is only 0.6% of that of the Earth. The atmosphere mainly consists of carbon dioxide. However, it also contains a small amount of methane (around 0.000001%) (ESA 2004). This is a puzzle to scientists because the ultraviolet light from the Sun should break up any methane within 600 years, and Mars is 4.5 billions old. Therefore there must be some process occurring on Mars which is constantly replenishing the methane.

Mars NASA

Mars- Image from NASA

There are various possibilities for the origin of this methane. One is that it is released by geological processes such as volcanoes or a chemical process occurring within rocks called serpentinisation. This is not as exciting as it sounds (no snakes, I’m afraid) – it is simply a slow chemical reaction between olivine (a mineral found on Mars) carbon dioxide and water which can produce methane.  Another is that there is a large reservoir of methane locked away in the ice below the Martian surface and as the temperature varies some of the ice may melt, thus releasing the methane into the atmosphere.

A fascinating possibility is that the methane is created by microorganisms below the planet’s surface.  On Earth more than 90% of methane in the atmosphere is produced by living organisms (ESA 2014). There are over 50 species of microorganisms known as methanogens that live off organic matter and produce methane as a waste product.  These microorganisms are found not only in wetlands (producing what is known as marsh gas) and in the soil but also in the guts of many animals such as cows and humans.  At the risk of sounding somewhat vulgar, the methane gas escapes from both cattle and ourselves in the form of flatulence.

methanogen

Methanogens

What will the TGO measure?

The TGO will measure how the methane content of Mars’s atmosphere varies with space and time. It will also be able to measure the concentration of other gases such as sulphur dioxide (which on Earth is normally associated with volcanic activity) and organic compounds such as ethane, methanol and formaldehyde (which on Earth are produced by living organisms).  Although the TGO won’t be able to say for definite what the sources of the methane found on Mars are, if the concentration of methane were found to vary with the seasons and also if methane were found in conjunction with other organic chemicals it would point towards a biological origin.

How long with the mission be?

The TGO is a joint mission between the European Space Agency (ESA) and the Russian Space Agency (Roscosmos).  The mission is described in more detail on ESA  (2016).  Now it has arrived at Mars it will spend a year gradually adjusting its orbit and by December 2017 it will be  in a low circular orbit only 400 km above the Martian surface where it will spend the next 5 years mapping the methane distribution.

 

 

References

ESA (2004) Mars Express Confirms Methane in the Martian Atmosphere, Available at:http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Mars_Express_confirms_methane_in_the_Martian_atmosphere(Accessed: 20 March 2016).

ESA (2014) The enigma of methane on Mars, Available at:http://exploration.esa.int/mars/46038-methane-on-mars/ (Accessed: 20 March 2016).

ESA (2016) Robotic exploration of Mars, Available at:http://exploration.esa.int/mars/46124-mission-overview/ (Accessed: 20 March 2016)

Schiaparelli on Mars.

On 14 March 2016 the European Space Agency used facilities at  Baikonur in Kazakhstan to launch their long awaited mission to Mars, the not so snappily named ExoMars Trace Gas Orbiter (TGO) and, bolted onto it, a smaller probe called Schiaparelli. Although the much larger TGO will only orbit Mars, next Wednesday, 19 October, Schiaparelli will attempt to land on the surface of of the planet, after its seven month journey.

schiaparelli-on-mars

What Schiaparelli might look like on Mars’s surface – Image from ESA

Assuming all goes well, the spacecraft will land on a flat area called Meridiani Planum, close to the equator. Currently this region on Mars is in its dust storm season. Dust storms occur often on Mars and can be very large, covering an area the size of the US, and may last for many weeks. During a dust storm the dust is so thick that it is not possible to see the Martian surface from Earth or even a spacecraft orbiting the planet. It also blocks much of the sunlight from reaching the planet’s surface. This was an important part of the storyline in “The Martian” where the hero’s car batteries were unable to move due to the lack of solar power, nearly stranding him.

Schiaparelli carries a collection of instruments called DREAMS (Dust characterisation, Risk assessment, and Environment Analyser on the Martian Surface), to study the Martian environment.

The DREAMS instruments will be able to measure the local wind speed and direction, humidity, pressure, atmospheric temperature, the transparency (or how the amount of light which which gets through the atmosphere varies) and atmospheric electric fields which may be caused by dust.  Unlike nearly all other spacecraft, Schiaparelli will have a non- rechargeable battery. The battery will only last for about a week, after which the spacecraft will run out of power and stop functioning. The decision to go for non chargeable battery was made because Schiaparelli is a relatively simple lander, with a small set of instruments and will have completed its mission within the week in which it will be operational. The main part of the mission, however, is a spacecraft which will orbit Mars for at least 6 years, and this is the TGO.

The aim of the TGO is to study how the distribution of the gas methane varies according to its position on the planet’s surface and over the course of time.

Trace Gas orbiter

Image from ESA

What is the significance of methane on Mars?

Compared to the Earth, Mars has a very thin atmosphere. Its surface pressure is only 0.6% of that of the Earth. The atmosphere mainly consists of carbon dioxide. However, it also contains a small amount of methane (around 0.000001%) (ESA 2004). This is a puzzle to scientists because the ultraviolet light from the Sun should break up any methane within 600 years, and Mars is 4.5 billions old. Therefore there must be some process occurring on Mars which is constantly replenishing the methane.

Mars NASA

Mars- Image from NASA

There are various possibilities for the origin of this methane. One is that it is released by geological processes such as volcanoes or a chemical process occurring within rocks called serpentinisation. This is not as exciting as it sounds (no snakes, I’m afraid) – it is simply a slow chemical reaction between olivine (a mineral found on Mars) carbon dioxide and water which can produce methane.  Another is that there is a large reservoir of methane locked away in the ice below the Martian surface and as the temperature varies some of the ice may melt, thus releasing the methane into the atmosphere.

A fascinating possibility is that the methane is created by microorganisms below the planet’s surface.  On Earth more than 90% of methane in the atmosphere is produced by living organisms (ESA 2014). There are over 50 species of microorganisms known as methanogens that live off organic matter and produce methane as a waste product.  These microorganisms are found not only in wetlands (producing what is known as marsh gas) and in the soil but also in the guts of many animals such as cows and humans.  At the risk of sounding somewhat vulgar, the methane gas escapes from both cattle and ourselves in the form of flatulence.

methanogen

Methanogens

What will the TGO measure?

The TGO will measure how the methane content of Mars’s atmosphere varies with space and time. It will also be able to measure the concentration of other gases such as sulphur dioxide (which on Earth is normally associated with volcanic activity) and organic compounds such as ethane, methanol and formaldehyde (which on Earth are produced by living organisms).  Although the TGO won’t be able to say for definite what the sources of the methane found on Mars are, if the concentration of methane were found to vary with the seasons and also if methane were found in conjunction with other organic chemicals it would point towards a biological origin.

How long with the mission be?

The TGO is a joint mission between the European Space Agency (ESA) and the Russian Space Agency (Roscosmos).  The mission is described in more detail on ESA  (2016).  Now it has arrived at Mars it will spend a year gradually adjusting its orbit and by December 2017 it will be  in a low circular orbit only 400 km above the Martian surface where it will spend the next 5 years mapping the methane distribution.

 

 

References

ESA (2004) Mars Express Confirms Methane in the Martian Atmosphere, Available at:http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Mars_Express_confirms_methane_in_the_Martian_atmosphere(Accessed: 20 March 2016).

ESA (2014) The enigma of methane on Mars, Available at:http://exploration.esa.int/mars/46038-methane-on-mars/ (Accessed: 20 March 2016).

ESA (2016) Robotic exploration of Mars, Available at:http://exploration.esa.int/mars/46124-mission-overview/ (Accessed: 20 March 2016)

Giving Venus an artificial magnetic field

As discussed in a previous post, in the far future humanity may decide to terraform Venus so that the planet has a similar temperature and atmosphere to that which currently exists on the Earth. However, the lack of a global magnetic field would cause significant obstacles to humans settling on Venus. Without this protective shield inhabitants would be exposed to the risk of serious illness if they ventured outdoor for a significant period of time. This post discusses how we could give Venus a planet wide magnetic field which, like the Earth’s magnetic field, would shield the planet from deadly radiation.

nasa earth mag field

The Earth’s protective shield- image from NASA

As many of you will know from your high school science lessons, when an electric current flows though a loop of wire it induces a magnetic field.

Mag field in Loop

So in principle, it would be possible to generate a magnetic field around Venus if we were to run a wire around the planet then pass an electric current through it.

However it wouldn’t be quite this simple. The strength of the magnetic field depends on the electric current through the wire and the diameter of the loop.

  • The greater the current or the smaller the diameter of the loop, the stronger the magnetic field is.
  • Alternatively, the smaller the current or the larger the diameter of the loop, the weaker the magnetic field is.

This inverse dependence on diameter means that if we were to pass a current of 10 amps (which is roughly the strength of current used by an electric fire)  through a massive metal ring which was the same diameter as Venus (12,100 km) because of the immense size of this loop the magnetic field generated would be around 100 million times weaker than the Earth’s field. To generate a planet-wide magnetic field of a similar strength to the Earth’s field, a current of 1 billion amps would have to be passed through the planet-size loop.

Venus Planet wide ring

This would be a truly enormous current to generate and maintain through such an immense structure. We could reduce the current needed by creating a coil or series of rings and the magnetic field from each individual ring would add up. If we were to construct a planet-sized structure of 10,000 separate rings then we would still need to pass a current of 100,000 amps through each ring. Maintaining such a current through this structure would require an enormous amount of power. If you have studied physics at high school you may recall that the power which is created as heat, when an electric current flows, is given by the equation below:

 power (in watts) = current squared (in amps)  x resistance (in ohms)

Where the resistance is a measure of the extent to which a material resists the flow of electricity. Resistance is measured in units called Ohms, named after the German physicist Georg Ohm (1789-1854).

Georg_Ohm

Wires and cables made out of good conductor such as copper have a low resistance and the thicker the wire the lower resistance.  If you were to make each of the 10,000 planet sized rings out a copper cable 20 cm thick, then the resistance of a metre  of the cable would be very low, only 0.000 000 54 Ohms. (See note 1). Even so, such a large current would mean that 5.4 kilowatts of heat would be generated per metre of cable.

However, this is only the heat generated for a single metre of cable. The total length of the 10,000 rings wrapped around Venus would be 400 billion metres. So the whole structure would generate an incredible 2,000 trillion Watts of heat. In the course of a year maintaining the magnetic field in this way would consume 18 million trillion watt hours of Energy. This is roughly 1,000 times larger than the entire Earth’s electricity consumption in 2014 (Enerdata 2016). If we were to generate this amount of energy by solar power, we have to cover an area of roughly 7 million square kilometers, which is roughly 70% of the area of the US with solar cells. See note 2.

USA Solar

It clearly be would be a significant challenge to generate enough electricity to create an artificial magnetic field in such a way. It would be a huge problem to remove all the heat generated, to prevent the copper coils getting so hot that they would overheat and melt.

A better way to do this would building the coils out of superconductors. I will discuss superconductors in more details in a future post. In essence superconductors are materials which have zero electrical resistance and thus zero losses to due to heat. An electric current can flow through a superconducting loop indefinitely. See Note 3. They were discovered in the early twentieth century and have many applications including maintaining the high electric currents needed to produce strong magnetic fields in medical devices such as MRI scanners and particle accelerators such as the Large Hadron Collider.

CERN

Large Hadron Collider- Image from CERN

Only certain materials can be  superconducting and, up until a discovery last year all superconducting materials only superconduct at very very low temperatures. This means that if we made the planet-sized ring out of superconductor, although there would be no power lost due to electrical resistance, a significant amount of power would need to be supplied to keep the structure very cold. If the cooling failed the material would no longer be superconducting and the magnetic field would disappear. Building such a massive structure of refrigerated planet wide rings would obviously present immense challenges, but these would not be insurmountable for an advanced civilisation able to terraform a planet.

High Temperature Superconductors?

When the first superconductors were discovered,  they only became superconducting close to close to absolute zero, which is the lowest possible temperature at -273.15 degrees Celsius . In the course of time new materials were discovered which superconducted at higher temperatures. However, most of the “high temperature” superconductors don’t support high currents and still need to be cooled to at least -200 degrees Celsius. A real breakthrough was made last year when it was discovered that hydrogen sulphide, the gas responsible for the bad smell in rotten eggs, became superconducting when cooled to -70 degrees, although it must be compressed to a pressure of 1 million atmospheres (Drozdov et al). This amazing discovery raises the possibility that in the future we will have room temperature superconductors, albeit at very high pressures, and perhaps these materials could be used to build a superconducting ring around Venus.

Another more radical option

As I mentioned in a previous post the reason that Venus does not have a magnetic field is because it has a slow rotation rate. In theory it would be possible for a highly advanced civilisation to increase the rotation rate of Venus to a rate similar to that of the Earth. This is such large topic that I will discuss it in a future post.

As a footnote – Artificial magnetic fields on Mars

Although this post is about creating an artificial magnetic field on Venus, the same considerations apply to creating to a magnetic field on Mars. The main difference is that because Mars is roughly half the diameter of Venus only half the current would be needed to create a magnetic field with the same strength as the Earth’s.

Mars Planet wide ring

The Science Geek.

Notes

 

(1) Assuming a resistivity of copper of 17 nano-ohm metres. This would give the resistance of a  1 metre length of the thick cable as 0.54 micro-ohms

(2) The calculation assumes that the average amount of solar radiation hitting a point on Venus’s surface over the course of a year is 700 watts per square metre and that solar panels can be mass-produced with an energy efficiency of 40%, which is much higher efficiency than today’s solar panels, which is typically 10-15%.

(3) All superconductors have a critical current density above which  the material no longer superconducts. This critical current depends upon the type of superconductor and the temperature.

References

Drozdov A. P., Eremets M. I., Troyan I. A., Ksenofontov V. and Shylin S. I. (2015)Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system, Available at:http://www.nature.com/nature/journal/v525/n7567/full/nature14964.html (Accessed: 24 April 2016).

Enerdata (2016) Global energy statistical yearbook 2015 – Electricity domestic consumption, Available at: https://yearbook.enerdata.net/electricity-domestic-consumption-data-by-region.html (Accessed: 6 May 2016).

 

Short post of the month – April 2016: Life on Mars?

On 14 March 2016 the ExoMars Trace Gas Orbiter (TGO) spacecraft was launched from Baikonur in Kazakhstan on a seven month mission to Mars. When it arrives at the red planet, it will study how the distribution of the gas methane varies according to position on the planet’s surface and over the course of time.

Trace Gas orbiter

Image from ESA

 

What is the significance of methane on Mars?

Compared to the Earth, Mars has a very thin atmosphere. Its surface pressure is only 0.6% of that of the Earth. The atmosphere mainly consists of carbon dioxide. However, it also contains a small amount of methane (around 0.000001%) (ESA 2004). This is a puzzle to scientists because the ultraviolet light from the Sun should break up any methane within 600 years, and Mars is 4.5 billions old. Therefore there must be some process occurring on Mars which is constantly replenishing the methane.

Mars NASA

Mars- Image from NASA

There are various possibilities for the origin of this methane. One is that it is released by geological processes such as volcanoes or a chemical process occurring within rocks called serpentinisation. This is not as exciting as it sounds (no snakes, I’m afraid) – it is simply a slow chemical reaction between olivine (a mineral found on Mars) carbon dioxide and water which can produce methane.  Another is that there is a large reservoir of methane locked away in the ice below the Martian surface and as the temperature varies some of the ice may melt, thus releasing the methane into the atmosphere.

A fascinating possibility is that the methane is created by microorganisms below the planet’s surface.  On Earth more than 90% of methane in the atmosphere is produced by living organisms (ESA 2014). There are over 50 species of microorganisms known as methanogens that live off organic matter and produce methane as a waste product.  These microorganisms are found not only in wetlands (producing what is known as marsh gas) and in the soil but also in the guts of many animals such as cows and humans.  At the risk of sounding somewhat vulgar, the methane gas escapes from both cattle and ourselves in the form of flatulence.

methanogen

Methanogens

What will the TGO measure?

The TGO will measure how the methane content of Mars’s atmosphere varies with space and time. It will also be able to measure the concentration of other gases such as sulphur dioxide (which on Earth is normally associated with volcanic activity) and organic compounds such as ethane, methanol and formaldehyde (which on Earth are produced by living organisms).  Although the TGO probe won’t be able to say for definite what the sources of the methane found on Mars are, if the concentration of methane were found to vary with the seasons and also if methane were found in conjunction with other organic chemicals it would point towards a biological origin.

How long with the mission be?

The TGO is a joint mission between the European Space Agency (ESA) and the Russian Space Agency (Roscosmos).  The mission is described in more detail on ESA’s website (2016).  When it arrives at Mars in October 2016  it will take around a year to get into a low circular orbit and then it will spend the next  5 years mapping the methane distribution. It will also have a lander module which will separate from the main orbiter and will land on the surface. The lander will measure the wind speed and direction, humidity, pressure and surface temperature, and determine the transparency of the atmosphere. It will also make the first measurements of electrical fields at the planet’s surface.

Next Post

I hope you have enjoyed this short post. In my next post I will be talking about the Earth’s magnetic field.

The Science Geek

 

References

ESA (2004) Mars Express Confirms Methane in the Martian Atmosphere, Available at:http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Mars_Express_confirms_methane_in_the_Martian_atmosphere(Accessed: 20 March 2016).

ESA (2014) The enigma of methane on Mars, Available at:http://exploration.esa.int/mars/46038-methane-on-mars/ (Accessed: 20 March 2016).

ESA (2016) Robotic exploration of Mars, Available at:http://exploration.esa.int/mars/46124-mission-overview/ (Accessed: 20 March 2016)