The sound of touchdown

Sensors in the feet of Rosetta’s lander Philae have recorded the sound of touchdown as it first came into contact with Comet 67P/Churyumov-Gerasimenko. The instrument, SESAME-CASSE, was turned on during the descent and clearly registered the first touchdown as Philae came into contact with the comet, in the form of vibrations detected in the soles of the lander’s feet.

Image credit: ESA/ATG medialab
Audio file credit: ESA/Rosetta/Philae/SESAME/DLR – CC BY-SA IGO 3.0

Note that this is an actual sound file; i.e. it is a recording of mechanical vibrations at acoustic frequencies. No modification was necessary except for some technical adjustments (e.g. the .wav format requires amplitude normalisation). Actual frequency content and duration are unchanged.

SESAME is the lander’s Surface Electrical Sounding and Acoustic Monitoring Experiment, and comprises three suites of instruments:


Focus on SESAME. Sensors are located in the three feet as well as in the units of the APXS (centre) and MUPUS-Pen (to the upper right of centre) instruments. Credits: ESA/ATG medialab

  • CASSE – the Comet Acoustic Surface Sounding Experiment, which allows mechanical parameters of the surface to be deduced, along with details of the structure of the subsurface;
  • DIM – the Dust Impact Monitor, which measures properties of impacting comet grains;
  • PP – the Permittivity Probe, which determines one of the key electrical properties of the material beneath Philae, which is linked to the water ice content of the surface.

Klaus Seidensticker from the DLR Institute of Planetary Research says: “Our data record the first touchdown and show that Philae’s feet first penetrated a soft surface layer – possibly a dust layer – several centimetres thick until they hit a hard surface – probably a sintered ice-dust layer – a few milliseconds later.”

Data from the SESAME-DIM instrument meanwhile suggest that current cometary activity at the final landing site is low, while preliminary data from SESAME-PP are consistent with a large amount of water ice under the lander. Combined with additional data from other instruments, the goal is to derive mechanical properties of the comet. However, first impressions already suggest that the surface of 67P/C-G is significantly structured, mixing soft and hard aspects.

Klaus adds: “At the moment, we are also supporting the effort to reconstruct the flight path of the lander after first touchdown, collecting all available data across the various instruments. This is important for SESAME, especially CASSE, as we need to know the speed, impact angle, and rotation rate before the first touchdown, but also the final landing place.”

SESAME Principal Investigators:
CASSE: Klaus Seidensticker (PI for the SESAME consortium), German Aerospace Center, Institute of Planetary Research, Asteroids and Comets, Berlin, Germany
DIM: Harald Krueger, Max-Planck-Institute for Solar System Research, Göttingen, Germany
PP: Walter Schmidt, Finnish Meteorological Institute, Helsinki, Finland



  • Alisson says:

    How this sounds are captured? Even that sound called "comet song"... It's only data that is converted in sound here in the earth via software?

    • ptr says:

      According to the post it's the mechanical movement of the feet touching the ground, captured by ten SESAME sensors:
      "Note that this is an actual sound file; i.e. it is a recording of mechanical vibrations at acoustic frequencies."
      The "comet song" as I understand it is oscillations in the magnetic field processed to be hearable.

    • This is actual, mechanical sound, conducted through the lander's feet--no different than how two astronauts and pressed their helmets together and allow speech to be conducted helmet to helmet, or how you can sometimes hear sound conducted through your bones.

  • Dave says:

    Are the measurements at the final landing site compromised in any way?.
    It looks from the picture we have seen of the landing site that at least 1 foot is not touching the ground.

  • DxB says:

    Unbelievable. If I am not mistaking this is the first sound ever recorded out of Earth?

    • rustam says:

      First sound was from Venera by Soviet station

    • daf09 says:

      Nope. You forgot about wind on Titan, which was recorded by Huygens during the Cassini–Huygens mission. Besides, that was a real sound, recorded with a microphone in Titan's atmosphere, not just a mechanical vibration, which one we've got here.

    • Philaezoph says:

      Remember ISS or the Moon landing or a lot of other things to remember like Sputnik or Kalinka where sound records have been made. To make history research is not boring but needs a lot more then the use of energy drinks.
      Some of those brands are supposed to give you wings but none of them claims to create wisdom for an obvious reason.

    • cheapopete says:

      Definitely the first sound recorded from a comet. :¬)

  • Crysknife007 says:

    My favorite part are the EM 'sounds' that the comet made:

  • Paw455 says:

    Sexy sound when you imagine it is from 500 mln km away from Earth.

  • No more useless information!
    We want REAL scientific results!
    Enough of this media soap opera episodes!

    • Jacob nielsen says:

      This is a scientific result. This recordind is not a gimmick, but will contribute in a mosaic to determine the composition of the surface of the nucleus. Is stated that the sound indicates a soft /dusty toplayer and a hard suface below. The sound you hear is transmitted through the landing gear and is composed of a 'springy' squeaky sound from the landing gear being loaded by the decelerating mass of Philae, flanked by a sound originating from the feet hitting and subsequently lifting a (flour like) substance. Our ears are not capable of resolving the timing of the element in this noise, but if you slow down the playback, and visualise (by the aid of spectral analysis etc.) a lot more information can be extracted: did the lander land on 1,2 or all three legs simultaneously? What is the density, thickness and mechanical properties of the toplayer? Etc. If you are not excited by this, maybe you should just wait till all this fun part is over in a few years from now. By then you should be able to get established facts, without the million bits of puzzling and some times incomprehensible, unconclusive, contradictory, missing () and boring bits of data.

      • Jacob nielsen says:

        But you are right about the 'media soap opera'. Somehow ESA has decided that the way to opproach the public, is to attract the attention of toddlers. Very puzzling at first, but then you realize that public outreach is also about attention in it self. Behind the scene, scientists are hysterical about protecting the propriety of their data. It approaches how God allegedly felt about the fruit of some tree in a walled garden ages ago.

      • Konrad says:

        Two thumbs up.

    • jhs says:

      oh - you are upset.
      Easy solution: dont visit this website.

      If you are interested in real scientific results:
      wait for presentations on conferences like the AGU and its reception in the media. Or wait a bit (weeks, months or years) for scientific papers ...

      And consder: presentation at scientific conferences might be preliminary and specualtive, even peer reveiwed papers might not be that what is accepted after some years as "the truth".

      Upcoming conference is the AGU fall meeting in frisco in a few weeks:
      You can already read abstracts :

      I must say for me it is interesting and exciting to see how information drops in - even it is (of course) selected stuff for the public. Bu tto be honest: Would you understand the stuff from the conference ?, e.g.:
      "... Consert ...: A Numerical Method for the Inverse Problem", or
      "The Shape of Comet 67P/Churyumov-Gerasimenko from Rosetta/Osiris Images " or
      "CONSERT Link Budget Simulator for the Direct Path"

      • Philaezoph says:

        Why wait ? You can do a lot of science right now. Although you might not always be successful enough to make it pay for your living. Still, enjoy the the stride.

      • CaptainJerry says:

        Please keep the data comming, mysteries, mistakes, and mayhem. It's called science. Indeed, we are all part of something wondrous thanks to the ESA!

    • masanori says:

      The more I have known about Philae the more I have surprised. One example is his instruments. Many have 2 or 3 roles on studying the comet. And, to be honest, some of the studies I got less interested. But I have huge interests in this one!! In fact, it's a complex sound. It means this sound contains many informations to study from, I'm sure! Congratulations SESAME team!!

    • It is useful information to others because in our case it provides important clues as to what the subsurface is composed of. In this case a very rigid material more than likely highly compacted crystalline silicates; cometary grains such as these at our website. These are 100 percent crystalline silicates and extremely compacted together almost welded together.

  • allen pollard says:

    Would it be possible to align the orbited to shine on the Lander?

    • Philaezoph says:

      Everything is almost possible but first lets set the corners of the playground. Have you found the spot to shine on?
      Have you a mirror for this purpose?
      No, there are no mirror like surfaces in the vicinity.
      No, whatever you use that is available is not going to reflect enough light on the lander, even if you knew where it is, to make any difference at all.
      So, mission impossible.
      But you might wait until next summer and by then ESA will be surprised as well. Its awake again and can do some tricks;)

  • Bominte says:

    Impressive ! It gives the feeling to assist at the landing event!
    Is that the recording of the sensor of a single foot ? It seems we can hear the two others with a delay and a bit weaker...

  • THOMAS says:

    After initial contact with the dust, it sounds to me much less like a dull "thud" than a real "whack", with several dying reverberations over the two seconds, as shown also by the sound wave oscilloscope. Surprisingly resonant, given the very low impact speed and the damping effect achieved by Philae's shock-absorbers.

    It will presumably be a relatively simple matter to simulate this sort of impact, in rigorous laboratory conditions, on different types of material (solid ice and different sorts of solid rock) and compare the experimental results obtained with the on-site CASSE recording.

  • W.R Taylor says:

    SLINGSHOTING AN ARROW AT A SPEEDING ROCK IN DEEP SPACE… (…and hitting it after a ten year long trajectory…)

    The European Space Agency's Rosetta project finally reached its target, by slingshoting an arrow at a speeding rock in deep space…and hitting it after a ten year long trajectory. That's quite an accomplishment.

  • Joao Prates says:

    Basic and probably dumb question: How can there be sound in space if we don't have air/atmosphere?

    • Petar Donchev says:

      Put fingers in your ears. You can still hear almost all sounds around you. But the sound now travel through your body. It is the same with Philae. Sound travel through its legs, body, comet surface, etc.

    • patrick barry says:

      It says it,it is vibration in the metal of the legs themselves.

    • Philaezoph says:

      you are smart enough to realise that there need to be something that the sound can travel through. The next step is to try to find out what the actual sound did travel through, this is a challenge and you will succeed soon enough.

  • James Coxhead says:

    How can a sound be hear on vaccum?

    • Jacob nielsen says:

      Technically it is not a sound, but a vibration in philae. Sure: no air, no sound.

    • Cometstalker says:

      Due to the huge amount of water and icebergs on this comet the lower atmosphere is foggy and therefore the sound spreads well

    • Philaezoph says:

      That depends on what side of the eardrums the vacuum is present,,,

  • rod says:

    the picture of Philae in shadow looks like it is travelling sideways--all the other images of the descent show a distinct spider shape --the 2 legs showing in the shadow pic are inline through the body of the craft.
    does the slight offset of the sound of the landing suggest that one leg hit s small object tilting the craft making it heavily hit the ground with the other 2 legs...sending it off at a tangent....Hey! just a thought ....Amazing adventure, the whole thing ---congratulations to you all!

  • daposter says:

    do you have the sounds of the other touchdowns?

    that's so cool 🙂

    you guys are awesome !

  • I-try says:

    I have the highest admiration for the achievements of the Rosetta and technical team to-date, and look forward to the future profound discoveries for Rosetta and Philae with confidence. That is providing there is no impact strike to either Rosetta or lander. Given the fact that both have functioned so well after travelling so long in such a hostile environment, it would require misfortune to disable them.
    Providing Philae is not located in a heat out-gassing vent that will increase in violence by the time rate of change of the inverse of the square of distance, that in turn is due to rapidly increasing gravitational acceleration, the increase in radiation from the Sun should be beneficial with regards to the eventual recharging of batteries.
    A careful comparison of the comets temperatures at similar distances from the Sun during approach and retreat will provide convincing evidence with regards to the physical validity of the Gravitational Thermodynamic Effect, which according to my work permeates the whole of physics; including variations to our weather.

  • Nicolas says:

    So, as I saw in this post, is it now confirmed that the ground is made of ice water?

    • Dave says:

      Th3e scientist on the first landing says
      ''probably a sintered ice- layer''

      on the final landing, he says
      '' consistant with a large amont of water ice under the lander''

      So he is getting there but it sounds like he has more work to do before he states it as fact.

      So no, its not confimed yet, lets wait for the figures.

    • THOMAS says:

      Not "confirmed", Nicolas.

      This press release only states that "preliminary data from SESAME-PP are CONSISTENT WITH a large amount of water ice under the lander".

      The expression "are consistent with" simply means "does not exclude the possibility of" a large amount of water ice under the lander. Rosetta mission scientists are still understandably clinging to the standard model which would have us believe that comets are "dirty iceballs" despite the images of what is clearly a largish lump of stratified rock and the fact that no "ice" has as yet been detected anywhere on the rocky surface.

      In other words, they are simply restating their faith that there is somehow ice somewhere beneath the surface. The "preliminary data from SESAME-PP" is also no doubt "consistent with" a very large amount of ROCK "under the lander". It's the rock we can see with our own eyes in the images Philae itself sent back to us from its final crash-landing point.

    • Dave says:

      The coment in the first reply should read The scientist on the first lands says
      ''probably a sintered Ice - dust layer''

      Sorry the original blog slightly miss quotes

  • Dave says:

    Is it also possible that the lander has picked up some ice on its surfaces on its trip through the coma. Could this have hampered the deployment of the anchoring mechanisms?

  • CL says:

    The sound is travelling through another medium (ie not a vacuum), in this case the comet. Put your ear on your desk and get some one to hit the other end with a hammer and you will get the idea of the principle 🙂

    • Philaezoph says:

      You are really trying to make people hurt them-self, never tell anyone that is not familiar to us dangerous tools to use those in a not foreseen manner. The sound must be reduced to a harmless level by holding a thumb between the desk and the hammer.

  • jhs says:

    Is this the sound from one feet or mixed from all three,
    or is it the sound recorded inside the main body ?

    On the grafical display on the soundcloud page it looks as if there are two channels, with the second one having much lower amplitudes - i.e. only two feets ?

  • Dr. Ruediger Hartung says:

    You're probably right. Besides this useless SiFi "Ambition" and data presented here in a hurry and partly wrong we are not far out in space but also off sience. Maybe it's a new type of twitter and youtube science generation, I really can't identify with. I am not willing to spend my taxes for such nonsense presented in here!

    • Philaezoph says:

      Its all about the degeneration of the humanity due to poor nutrition and all those imaginary reality devices. Working ants need not a lot of brains to do a proper job as long as 98 % of them keep in track. Read those blogs and soon realise that it is a huge research value alone in the variety of the capacity behind those persons and their thoughts from almost no clue at all about anything to experts in everything.

  • If you were standing on the comet when Philae landed, you would not hear anything because of lack of atmosphere. You might feel the vibration through your feet.
    However, the "sound" that is being played is the vibration detected by the sensors which is being made audible by playing it through the sound card on your computer.

  • Jonboy says:

    Look up the Huygens lander which parachuted onto Titan a few years back, think there was some audio recording taken during the descent to the surface.

  • Татьяна Новикова says:

    Любые звуки Космоса - прекрасны, многозвучны и необычны. Здорово, даже не верится, что можно все это слышать. У меня много в записи космических звуков с сайта NASA. Очень красивая "музыка" С благодарностью из России. Any sounds of Space - nice, mnogozvuchni and unusual. Cool, I can't believe you all to hear it. I have a lot to write cosmic sounds from the NASA site. Very beautiful music. With thanks from Russia.

  • ed-cher says:

    i'm just wondering how does sound propagate through vacuum?

  • Robin Sherman says:

    It sounds to me like Philae landed on a blanket covering a pile of broken crockery.

  • Tim Burns says:

    It seems to me that every scientist, no matter his or her discipline, should be more than willing to wait for the data to be published before sounding so cynical and so critical. Are we not all in this, scientific research that is, for the betterment of mankind? How does trashing this mission, or trying to upstage the results without the proper data, following this mantra? Lighten up World of Science, and show some support for these scientists! Some of these people have put their entire scientific integrity and careers on the line here. Show some love and drop the jealousy and hate!

    • Alembe says:

      Well said, Sir.

    • Retired says:

      This is science, yes. Support is present, we all pay taxes.
      Scientist? You name them if you see them, so far managers and non experts are on public display. I see no result from research. What i see are shrapnels of unsorted data that are of only minor value. The essence is not displayed and will only reach those who have a deep interest in a few years and most likely making their semesters on some university. Those researchers at the treasure-box right now are not likely the very best for the purpose but by chance the first to have a go. wish them the best of suchsess with their effort. To make something for humanity at large is not the goal of this kind of missions as the majority of mankind have other priorities than space research. Out of 8 billion individuals only a small fraction will gain anything at all. What will you or your children gain? At least my five children are well educated and know what is important in this life on this planet. ESA is only for curiosity at large and for those few employed a way to make a living in an interesting high tech group of companies. This blog is to ESA just about what flee is to dog. You, me and the 500-50000 that visit these blogs are really a minority, almost to be called an endangered species. To get some perspective is essential in space research.

  • Es también posible que el módulo de aterrizaje se ha recuperado un poco de hielo

  • nice undamped oscillation, hope my sampler/sequencer gets in love with rosetta, of course it will be new music, never heard before, hope i find enough time to let the machines run and select the beautiful messages in this vibe of machines.

  • james says:

    It sounds more of a crash! Plus how did you record a sound with no air to carry it? Silly!

  • james says:

    It sounds more of a crash! Plus how did you record a sound with no air to carry it?

  • MC says:

    I think it is amazing that I can be part of this ''media soap opera episodes''. I find it exiting the fact that this little washing machine size like is millions of miles away from us . It could have been lost in space , hit by something , you name it but after 10 years of traveling go there. .I really share their exitment. Lets just enjoy this . My congrats to all peole involve in this amazing project .

  • mfe says:

    Philaezoph! That's enough! Play nicely with the other children!

    • Philaezoph says:

      Hi mfe, thanks for the notice, i will strain myself not to be too sarcastic but its a struggle and after all, my worst comments don't pass the sieve of censorship. No harm done and all this so called science is anyhow not to be taken seriously. Its nothing more then an entertainment an as far from education and proper pedagogic urge as can be.

      I would humbly suggest that there would be at least one full story per month whit a head, body and tail.

      One simple example would be to describe how the comet so far has developed its coma from the first sighting up to right now in an absolute and not relative term and how much the size and mass of this coma is due to captured solar wind and to what properties its dust and vapor from the comet due to solar radiation respectively the out bursts or if you believe in any orher processes that removes material from the nuclei and add this to the coma.
      After all the coma is the one thing of the comet that really is a great part of its essence.
      Asteroids, planetoids and planets do not develop fast in the human time scale, comets are a lot more active and change their behaviors rapidly enough to be noticed on a weakly schedule once getting within a range for proper observation and this time the range is about a nosy sort of distance.
      Its absolutely useless to just present some raw data as >90% of the readers have no clue what di-hydrogen-monoxide means. Or what is the vacuum around the comet actually, in term of particles in a volume of a refreshment tin-can compared with the amount of what is to be found in an emptied can on earth.

      Something simple but still with a flavor of science that takes about 5-10 minutes to read.
      Is this too much asked for?

      To claim that there will be data released in two years due to the fact that if this would happen too soon then some researchers would end up at the end of the career line is nonsense.

      To give some persons, projects to present a story that enlighten the educable part of the public is a way to increase the value of ESAs PR account, that about now is getting watered down for each publication, is a serious issue.

  • Cometstalker says:

    “Our data record the first touchdown and show that Philae’s feet first penetrated a soft surface layer – possibly a dust layer – several centimetres thick until they hit a hard surface – probably a sintered ice-dust layer – a few milliseconds later.”

    So if the speed is 1m/s then every cm represents 10 milliseconds. Several centimeters dust represents 20 to 50 milliseconds and is a bit more then a few milliseconds.

    First of all the majority of the sound is a mechanical rattle of the landers foot, also notice that this device was supposed to absorb the energy of the impact with an electromechanical servo-controlled chock-absorber and this was only compressed 4 cm. If it would have worked properly at least 40 cm compression would be expected. A system failure was present and this launched the lander into another 2 hour of flight. The impact energy was mostly absorbed by the comet surface and the contact of the lander with the comet was less then 300 ms. The rest of the sound is the rattling of the landers foot after the debounce. You can even see the oscillation frequency of the "landing gear".

    No thruster, no twin harpoons, no chock-absorber.
    This is quite messy in a lot of view points, at my opinion. It would be really nice if someone from the mission control would make a statement how and why so many systems failed. Im not trying to nail somebody to the wall but the failures are also a part of this mission and could be filed in a public report with some sort of conclusions. So far the barebones is what we get and those have discrepancies.

  • njouba says:

    think you ESA contribution to understund the space
    Rosetta is the dream , it`is very nice

  • baki says:

    think you ESA contribution to understund the space
    Rosetta is the dream , it`is very nice


    Congratulations so much!!!!!!!!!!!!

  • Dimon says:

    I think it's the great achievement to land on a comet. So this sound is the remarkable detail of such considerable event

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