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The biggest source of methane here on  earth is flatulent cows that's right  

cow burps and cow farts. Now the methane  technically doesn't come from the cows themselves  

but from the microbes that live in their gut that  help them digest all of the plants that they eat.  

Once the digestion is done the cows pass the  methane gas and it enters our atmosphere and  

becomes a greenhouse gas and contributes to  global warming. But what has that got to do  

with mars? Well because of its connection to life  here on earth it's been considered for a long time  

a potential biomarker - a signature that life, at  least microbial life, might be present on another  

planet. Science is never that simple though  because methane can also be produced in geological  

processes, you know by rocks. So when the first  detection of methane in the martian atmosphere  

was made back in 2014 people were obviously  excited but also cautious as well you know  

we had to repeat the experiment we'd need more  measurements from other satellites and rovers and  

landers to confirm whether methane had actually  been detected. Little did they know then though  

that all those extra measurements would just lead  to even more confusion and a scenario that we're  

only just beginning to explain. Kind of like  a science whodunnit this is the story of the  

here on earth. In 2019 the methane concentration  in the earth's atmosphere was measured at 1886  

parts per billion per volume. On Mars it's more  like one part per billion per volume. To put that  

into context it's like a little pinch of salt  in an olympic sized swimming pool and that's  

not even a real exact measurement it's actually  what we call an upper limit. Essentially we know  

the methane has to be less than that otherwise  we would have detected it in all the experiments  

that have been run over the years either with  telescopes here on the ground or satellites in  

orbit around mars. And even curiosity rover when  it landed on mars in 2012 it put a limit on the  

amount of methane in the martian atmosphere of  0.5 parts per billion per volume - that's barely  

anything right? It's nothing to write home about  so off curiosity when doing other things but then  

in 2014 curiosity detected spikes in the  methane concentration over the span of about  

two months the average out at about 7.2 parts  per billion per volume and it's also seen the  

normal concentration of methane changing with  the seasons as well. That means something  

on mars is producing methane seasonally but  also with these random spikes as well and we  

just don't know what it. Monica: "It just got  interesting!" Now since 2018 a satellite that's  

in orbit around mars ESA's ExoMars trace gas  orbiter has been continuously searching for  

signs of atmospheric methane now the methane  detector on exomars is supposed to be the  

gold standard for detecting methane it's used in  industry on earth loads it's also used on the iss  

as well to give advanced warning to astronauts  if there is like a methane leak or something.  

But on mars this gold standard detector didn't  detect any methane in the martian atmosphere  

and so curiosity's detections of seasonal  variation and random spikes were then massively  

brought into question if the thing that's like the  gold standard didn't detect anything. Now ExoMars  

is only sensitive to methane above about three  kilometers in altitude in the martian atmosphere  

and also its limit on the amount of methane it  can detect is only five parts per billion per  

volume. You might be thinking well what curiosity  detected was lower than that but the problem is  

if this methane is perhaps being released let's  say by the martian rocks or something like that  

at the surface continuously, and curiosity is able  to detect that amount that is being pumped out,  

that should slowly build up in the atmosphere,  get well mixed and should get above concentrations  

that ExoMars should then be able to detect.  But that's not happening. At the rate that  

curiosity is detecting at the ground, if you  assume that that's what it's pumping out,  

it should have built up to a concentration  that exomars can detect in about 28 years! It's  

*highly unlikely* that these methane emissions  from the ground have only just started in the  

past 20 years or so when curiosity just happens to  have landed on mars when mars has been around for  

4.5 billion years. So once again that leaves  us with this discrepancy between what curiosity  

measures and what ExoMars measures - it's a  classic science mystery that needs solving. And  

so the curiosity team especially put their heads  together and were like "what could be the possible  

explanations for what we've seen?" and the first  thing they started with was "is the rover itself  

giving out this methane?" Perhaps by rolling  over rocks and crushing them and releasing any  

trapped gas but the spikes in methane it detected  didn't correlate with any movement of the rover,  

the rover was always still when it took those  measurements, so that was quickly dismissed.  

Then the next idea was well could there be  some methane leaking from other instruments  

and detectors within curiosity rover itself?  But you know every system was double and triple  

checked and they're pretty sure there's no methane  leaking from the rover. The next idea was whether  

these methane spikes perhaps correlated with like  a direction that the rover was facing in perhaps  

towards like a certain rock formation or something  that might just be a very high concentration  

of methane but again no there was no correlation  there. And similarly there was no correlation with  

wind direction either, perhaps the wind bringing  something over from a very high concentration  

of methane somewhere. All of those ideas were  thrown out but then one of the curiosity team  

scientists Dr John Moores had an idea and he said  in an interview with nasa that he took: "a very  

canadian way of looking at this" and said: "what  if both curiosity and ExoMars are both right?"  

I just love this very canadian way of looking  at things! Because they realized there was  

a correlation with the time of day that the  measurements were taken. Up until 2019 all the  

methane concentration measurements that curiosity  had made had happened at night when there wasn't  

much else going on with the rover. So what the  team did was then measure the concentration of  

methane during the day and noticed that it was  much lower it dropped to 0.05 parts per billion  

per volume down from the 0.5 parts per billion per  volume that averaged out over the night time. So i  

guess that's kind of like a 10% of a pinch of  salt in an olympic swimming pool - scientists  

should never write recipes i'm just gonna put that  out there! And guess what the ExoMars satellite  

had only ever taken its methane concentration  values during the day because it physically  

needs sunlight in order to be able to make the  measurements. So all of those measurements the day  

and the night concentrations have been explained  in a paper published recently by Webster and  

collaborators, which i'll link in the description  below if you want to check it out. And the way  

they've explained this day night difference is due  to the weather essentially. So at night it's much  

cooler the atmosphere is much calmer and methane  seeping from the rocks, due to whatever process,  

is building up at the surface essentially. But  when the sun rises it starts to heat up the air  

and then that sets up a classic weather pattern of  hot air rising taking the methane with it and then  

cold air falling and that mixes it all up in the  atmosphere lowering the concentrations to below  

what ExoMars can detect during the day. So that  study at least gives us one possible explanation  

for the discrepancy between the curiosity and the  ExoMars measurements but it still leaves a whole  

boatload of other unanswered questions the first  of which just being what is producing this methane  

on mars? Especially these weird spikes and this  seasonal variability which is to be honest just  

weird. Although given the fact that the weather  explained the last problem it's likely that  

something to do with the sun and solar radiation  could explain the seasonal variability as well.  

Perhaps in the summer there's more incidence  of solar radiation that melts some ice trapping  

methane gas that's perhaps trapped underground,  so we don't know how it's gotten underground  

whether it is just coming from rocks or maybe  there's some microbial life living underground  

there perhaps releasing methane we just don't  know. The second question that still remains  

is why isn't this methane, which is coming from  rocks or microbial life we don't know, why isn't  

this methane building up in the atmosphere over  time? Curiosity landed in Gale Crater and that's  

where its detected these higher concentrations  of methane at night and including these spikes  

as well. Now we don't think there's anything  special about gale crater if gale crater is  

emitting methane then probably the rest of mars is  too so it should have built up to concentrations  

that ExoMars can detect but it hasn't. Now  we know that methane is stable in the martian  

atmosphere for at least 300 years before it does  get broken down by the impact of solar radiation,  

but 300 years is still enough time for it  to build up to concentrations that ExoMars  

can detect. So there must be something else, some  other process going on, that is somehow destroying  

the methane. And whether that is perhaps you know  just reabsorption by rocks of the methane? People  

propose the idea that static electricity generated  by the dust storms and sandstorms, that we see  

engulf mars occasionally, could actually be  creating static electricity that could destroy  

the methane. Or perhaps maybe it's reacting with  oxygen in the martian atmosphere as oxygen is  

very reactive and perhaps that's getting rid of  the methane. There's lots of ideas but we still  

don't know which one is actually happening.  Either way like whatever is happening on mars  

this study that's come out this month has at least  given us one piece of this very confusing puzzle  

but rest assured there is still a whole heap, a  truckload, of unsolved martian methane mysteries!

Before we get to the bloopers a huge  thank you to this week's video sponsor  

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opportunity to learn and for continuing to support  this channel. But now roll those bloopers...

was one thousand eight hundred and sixty six parts  pavilion, parts pavilion? parts per billion per  

volume - i'm going to trip over that so much in  this. On mars however the methane concentration is  

more like one parts pavilion... pavilion?! oh my  god i said it again parts per billion per volume.  

It put a limit on the amount of methane  in the atmosphere of 0.5 parts pavilion...

And it can only measure down to about 5 parts  pavilion per volume - pavilion?! Why?! WHHHYYYY?!