Venus Monitoring Camera image taken in the ultraviolet (0.365 micrometres), from a distance of about 30,000 km. Credits: ESA/MPS/DLR/IDA

Was Venus Once a Waterworld?

Article Updated: 24 Dec , 2015
by

[/caption]

Ever read Isaac Asimov’s 1950’s novel “Lucky Starr and the Oceans of Venus”? Maybe Asimov wasn’t so wrong about Venus after all. Analyzing data from ESA’s Venus Express, planetary scientists are looking at the possibility that the planet may have once harbored oceans, and potentially could have been habitable when during its early history.

While Earth and Venus are comparable in size, they otherwise seem completely different. Earth is a lush, clement world teeming with life, while Venus is hellish, its surface roasting at temperatures higher than those of a kitchen oven.

The biggest difference between the two planets is that Venus has very little water, while Earth is bathed in it. Were the contents of Earth’s oceans to be spread evenly across the world, they would create a layer 3 km deep. If you were to condense the amount of water vapor in Venus’ atmosphere onto its surface, it would create a global puddle just 3 cm deep.

But scientists are beginning to think that billions of years ago, Venus probably had much more water. Venus Express has confirmed that the planet has lost a large quantity of water into space, by measuring the rate of how much hydrogen and oxygen is escaping into space, as the Sun’s ultraviolet radiation beats down on the planet and breaks up water molecules.

Venus Express has measured the rate of this escape and confirmed that roughly twice as much hydrogen is escaping as oxygen. It is therefore believed that water is the source of these escaping ions. It has also shown that a heavy form of hydrogen, called deuterium, is progressively enriched in the upper echelons of Venus’s atmosphere, because the heavier hydrogen will find it less easy to escape the planet’s grip.

“Everything points to there being large amounts of water on Venus in the past,” says Colin Wilson, Oxford University, UK. But that does not necessarily mean there were oceans on the planet’s surface.

Eric Chassefière, Université Paris-Sud, France, has developed a computer model that suggests the water was largely atmospheric and existed only during the very earliest times, when the surface of the planet was completely molten. As the water molecules were broken into atoms by sunlight and escaped into space, the subsequent drop in temperature probably triggered the solidification of the surface. In other words: no oceans.

Although it is difficult to test this hypothesis it is a key question. If Venus ever did possess surface water, the planet may possibly have had an early habitable phase.

Even if true, Chassefière’s model does not preclude the chance that colliding comets brought additional water to Venus after the surface crystallized, and these created bodies of standing water in which life may have been able to form.

There are many open questions. “Much more extensive modelling of the magma ocean–atmosphere system and of its evolution is required to better understand the evolution of the young Venus,” said Chassefière.

When creating those computer models, the data provided by Venus Express will prove crucial.

The Venus Express team are meeting this week to discuss their latest findings at the International Venus Conference in Aussois, France.

Source: ESA

,



25 Responses

  1. William928 says:

    Water, water everywhere! What’s next, water on Mercury? It seems these possible discoveries lead us closer to the conclusion that life existed elsewhere in the Solar System at some point in its history, and may still on Enceladus, Titan, or another moon.

  2. flogger11 says:

    ^^Not to mention the rest of the galaxy William!

  3. etlan says:

    All you want to say is : The Universe is Wet. Ok, but you earthlings are amazingly obsessed with life as you know it: barionic-dipole-field-dna based kind. Ironically you despise the most common and ubiquitous proof-like form of data that you have about non-barionic mode of life processes: what your ignorant and credulous peers call “afterlife”. We know you like it in a scientific higher ground: physically detailed and elegant observations. The non-problem is that you just seem ludicrous all along talking that way,

  4. Jon Hanford says:

    Could the lack of a intrinsic magnetic field possibly play a role in how Venus appears to us today?

  5. IVAN3MAN_AT_LARGE says:

    @Jon Hanford,

    Affirmative. See “Where did Venus’s water go?“:

    […] ¶ Unlike Earth, Venus does not generate a magnetic field. This is significant because Earth’s magnetic field protects its atmosphere from the solar wind. At Venus, however, the solar wind strikes the upper atmosphere and carries off particles into space. Planetary scientists think that the planet has lost part of its water in this way over the four-and-a-half-thousand million years since the planet’s birth. ¶ […]

  6. IVAN3MAN_AT_LARGE says:

    Also, see “[Venus] caught in the wind from the Sun“:

    […] ¶ The Sun has probably been stripping away the Venus’ atmosphere throughout the planet’s four-thousand million-year history. Unlike Earth, Venus does not possess an intrinsic magnetic field to protect its atmosphere from the solar wind, a constant stream of electrically charged particles emitted by the Sun. Instead, the solar wind interacts directly with the upper atmosphere of Venus. ¶ […]

  7. Paul Eaton-Jones says:

    An early habitable phase does not imply that life even dreamed of starting there. I’ve read that there might be fossilised microbes lurking on Venus. Evidence of water doesn’t mean evidence of life. The phrase ‘clutching at straws’ springs to mind.

  8. StockportJambo says:

    @Paul

    The fact that life exists on Earth anywhere where this is both water and an energy source means that the “search for life” was redefined some time ago as the “search for liquid water”. It is a natural assumption to make… based on the available data we have.

    It is, however, completely wrong.

    Life may exist on the sub-surface oceans of Europa, or underground on Mars, or even Venus long ago if there was water there. But really we only need some kind of fluid solution for the chemistry of life to play out. See the latest articles on Titan for an example of what I’m saying. The problem is we only have one model to go by – life on Earth and DNA… not enough to make assumptions across something the scale of the Universe. And not enough people prepared to think outside the box.

    Alien life may not need water, or even be built from amino acids, proteins, or other “organic” molecules. We probably wouldn’t even recognise it as “life”. Silicon based life would probably look like a rock.

  9. Jon Hanford says:

    @IVAN3MAN,

    Thanks for those links. I didn’t see mention of this in the article above, but had a recollection of this stripping process being mentioned elsewhere. Mars, too, seems to have undergone a similar process IIRC.

  10. Torbjorn Larsson OM says:

    Could the lack of a intrinsic magnetic field possibly play a role in how Venus appears to us today?

    Possibly, but it seems notoriously difficult to get hold of quantitative numbers. For example, IIRC Venus looses on the same order of magnitude gas as Earth under solar wind stripping. The closer in field also means a smaller surface to interact through.

    Mostly what protects an atmosphere is the presence of an atmosphere. And Venus has a good supply of that.

    IVAN3MAN provided articles that indicate that solar wind interaction may be the culprit, but that it remains to be tested.

    Summing it up AFAIU, the solar wind is the likeliest culprit, it remains to be verified, and it remains to be seen if the total loss can predict the water content of Venus under some scenario of initial content.

  11. Torbjorn Larsson OM says:

    not enough people prepared to think outside the box.

    I can’t agree with that assessment, because people are indeed researching the alternatives. For example, otherwise the Titan surface loss of hydrogen, acetylene, possibly ethane and the difference in carbon isotope ratio compared to the other Moons wouldn’t be proposed to have a biogenic explanation.

    But water is both the most common liquid and the one best suited to life. Non-polar solvents such as methane or ethane doesn’t do well with organics, making it that much harder to make cells for example of a common and useful biological structure; possibly impossibly hard.

    [Speaking of which, we have enough difficulty to understand how water-based life got started in the first place.]

    Considering that it makes sense to concentrate on water in the near space environment.

    If it is any consolation, the astronomical search for exoplanet biospheres will have to take a “solvent free” approach (or nearly so), since it will look on skewed thermodynamical balances such as the presence of free oxygen.

    We probably wouldn’t even recognise it as “life”. Silicon based life would probably look like a rock.

    Now you are using the NASA definition, which is good for swift recognition of cellular life (confined metabolism) but not for life in general; for example, viruses isn’t life under that definition.

    Any evolving population would be life by the widest possible definition. But we are only interested in biochemical substrates here, so let’s forget about software and hardware and concentrate on wetware. Still, that means there are no intrinsic difficulties in recognizing alternatives to our own evolutionary results.

    Silicon life likely doesn’t exist though. Since silicon dioxide is a mineral, it would be constrained to the reductive half of the energy levels. (As Titan life would be.)

    However, while the end product on that side, silane (silicon tetrafluoride) and its relatives, are gaseous under a wide enough temperature range so amenable for gas exchange biology, they react violently with water. Silicon life would self combust in ordinary atmospheres. So no dice.

  12. Torbjorn Larsson OM says:

    D’oh! I can’t believe I wrote that! Silane is silicon tetrahydride, of course! Oh, woe…

  13. Aodhhan says:

    More accurately… why couldn’t (past or present) Venus have water on it?

    I highly doubt its current orbit is where it has always called home; even more likely it once kept a more eliptical trek around the Sun.

    It has already been proven Earth had water early in its history, so it is very easy to translate this to Venus as well.

    Life on Venus can be debated just as well. Does it have it today? Likely not. Not because it is too hot, or not enough water… but for the simple fact there is too much radiation.
    Although we’ve seen life thrive in some pretty wild extremes; it is a little hard to imagine life being able to take off when little shards of subatomic particles are knocking off protein, enzymes, dna, carbon–silicon bonds, and/or anything else required to be kept safe from such muonic artillery.

  14. Kevin says:

    No Kevin Costner jokes?

  15. Hon. Salacious B. Crumb says:

    Aodhhan personal theories again returns…

    I mean “…when little shards of subatomic particles are knocking off protein, enzymes, dna, carbon–silicon bonds, and/or anything else required to be kept safe from such muonic artillery.

    Eh? What utter nonsense yet again. Obviously Ultra-violet light has more effect on life and damage to organisms than the effects of sub-atomic particles.

    Moreover, did ancient Venus have ozone in it atmosphere? What was the composition of atmosphere?

    Life would be required to exist to up the oxygen level. If Venus did not have life, this might explain why the carbon dioxide is so prodigious in the atmosphere today. The water was slowly converted into mostly the carbon dioxide. There was simply no life for the carbon dioxide to be converted to oxygen.

    As for; “I highly doubt its current orbit is where it has always called home; even more likely it once kept a more eliptical trek around the Sun.” That might be lively, but in fact, all the inner planets, would have had similar changes – include our Earth. If it was more elliptical – so what! Your warped logic, these changes were significant on Venus and no Earth, but what has this anything to do with water, eh? The whack- job Immanuel Velikovsky theories make more sense than what you say!

    All you have proven is you don’t have a clue what you are talking about – yet again. Go do some reading – you might learn something instead of wanton hearsay.

  16. Torbjorn Larsson OM says:

    @ Aodhhan:

    too much radiation … muonic artillery

    What radiation? Muons result from cosmic radiation (CR) AFAIU, due to the energies required.

    – CR would be slightly more intense for Earth, the solar magnetic field is shielding CR over interstellar distances. I.e. CR is predicted to be more intense in interstellar space AFAIU. But essentially the same at Venus as at Earth, I think.

    – CR is a typical example of how magnetic fields aren’t the one all shield for planets. It is the atmosphere integral (summed up) mass that shields us from CR (on land). And Venus will do much better in that regard.

    – UV acts more damaging for biology than ionizing radiation as it breaks bonds big time. Being ionized isn’t an immediate problem for a biomolecule, and surrounding water would fix it swiftly. Being broken apart or otherwise chemically modified is a problem.

    Biomolecules with aromatic rings acts as antennas for UV; one has only to think of the many pigments and photosynthetic systems to recognize the basic light interaction trait.

    Actually pigments show that UV is a problem for organisms, while ionizing radiation isn’t. We have developed such for UV protection on land, say, in humans, while typical non-pigment animals are water or cave dwellers.

    Added to that both amino acids and nucleic acids show signs of being photoselected under UV. This is, in the Zn world scenario, due to that aromatic rings collect and swiftly dissipate the resulting thermal energy to a substrate before radiation damage occurs. This is supposed to predict why PAH on dust is a common occurence in space. (Though I believe that particular prediction has some problems.)

    I don’t see why Venus, given roughly the same starting conditions, wouldn’t have had life early on. The question is when and why it went down another geological pathway. According to the latest findings of old geology structures maybe we will eventually be able to have an answer, and then know if life was a possibility there.

  17. Torbjorn Larsson OM says:

    It hits me that my description of biomolecules under ionizing radiation is too facile; it is at a guess mostly the ubiquitous water that gets ionized in the first place.

  18. Torbjorn Larsson OM says:

    D’oh! “due to that aromatic rings collect and swiftly dissipate the resulting thermal energy” – due to that aromatic rings collect light (or, more generally, excited states from other parts of the biomolecule) and swiftly dissipate the resulting thermal energy.

  19. Hon. Salacious B. Crumb says:

    Coawrdly Aodhhan, as usual, disappears when the going gets tough.
    Criticises like crazy but can’t hack the facts. So pathetic.

  20. Lawrence B. Crowell says:

    This is an interesting speculation, but I am not certain this can be verified easily. It is my understanding that the Venusian crust chaotically recycles itself every few hundred million years. Venus goes through periods as a complete magma planet. This probably erases much information about ancient oceans. We may never get any clear idea of Venusian history, where in contrast with Mars we might get at least some accurate sketch.

    We had some discuss about putting robots or rovers on Venus. It might be possible, but I shudder at the cost. Venus from a cost-benefit perspective is probably going to be shrouded in thick atmospheric mystery. To be honest if given a choice between some program to probe gravity waves beyond the CMB, or putting robots on Venus I would have to go with the first.

    LC

  21. Torbjorn Larsson OM says:

    Venus goes through periods as a complete magma planet.

    Not according to the latest research. Ribbon tessera terrain (RTT) “represents some of Venus’s oldest surfaces, and is widely accepted as forming prior to postulated global catastrophic resurfacing.” Apparently “~30% of Venus has rtt exposed at the surface or shallowly buried (>0.75 km).”

    This challenges the catastrophe hypothesis. Now, as a layman I don’t know if any of this is good. Apparently it is an old controversy in the background, where the terrain imagery interpretation from the Magellan onwards of no large craters have been challenged by researchers like Hamilton:

    “Conventional analyses assign to a fraction of the most distinct old structures origins by plumes, diapirs, and other endogenic processes, and ignore the rest. […]

    A continuum of increasing degradation, burial, and superposition connects the younger and truly pristine young impact structures with the most modified of the ancient structures. Younger craters of the ancient family are superimposed on older ones in impact-definitive cookie-cutter bites and are not deflected as required by endogenic conjectures. Four of the best-preserved of the pre-“pristine” circular structures are huge, with rimcrests 800–2000 km in diameter, and if indeed of impact origin, must have formed, by analogy with lunar dating, no later than 3.8 Ga. Much of the venusian plains is seen in topography to be saturated with overlapping 100–600 km circular structures, almost all of which are disregarded in conventional accounts. Several dozen larger ancient plains basins reach 2500 km in diameter, are themselves saturated with midsize impact structures, and may date back even to 4.4 Ga.”

    Of course, eventually these protracted to and fro’ risk devolving into meaningless pattern recognition. Without being able to read the paywalled away papers, the RTT evidence sounds a bit more promising.

    My layman take FWIW (i.e. not much): Extraordinary claims like catastrophic resurfacing, not seen anywhere else to my knowledge, needs extraordinary evidence. However, apparently the evidence is even less than ordinary to some. At the very least it seems like an open question?!

  22. Aqua says:

    Enigmatic Venus may soon reveal some of her long hidden/veiled secrets as current and future missions gather and send back data…

    1) Why does Venus rotate backwards?
    2) Why is that rotation so slow?
    3) What has caused the surface to be continually ‘reworked’?
    4) What conditions created its sulfuric acid atmosphere?
    5) Why doesn’t Venus have a magnetic field like Earth?
    6) What happened to the water on Venus?
    7) Did Venus ever harbor life?
    8) How were the strangely flattened volcanic landforms created?

    The list friends, goes on and on… WHICH is why we’ve gone there and will go there again and again.

  23. Torbjorn Larsson OM says:

    3) What has caused the surface to be continually ‘reworked’?

    That is possibly a matter of some contention, which would have been more clearly seen and possibly discussed if ever my previous comment gets out of moderation.

    I’ll repeat it here but without the offending links then:

    Venus goes through periods as a complete magma planet.

    Not according to the latest research. Ribbon tessera terrain (RTT) “represents some of Venus’s oldest surfaces, and is widely accepted as forming prior to postulated global catastrophic resurfacing.” Apparently “~30% of Venus has rtt exposed at the surface or shallowly buried (>0.75 km).”

    This challenges the catastrophe hypothesis. Now, as a layman I don’t know if any of this is good. Apparently it is an old controversy in the background, where the terrain imagery interpretation from the Magellan onwards of no large craters have been challenged by researchers like Hamilton:

    “Conventional analyses assign to a fraction of the most distinct old structures origins by plumes, diapirs, and other endogenic processes, and ignore the rest. […]

    A continuum of increasing degradation, burial, and superposition connects the younger and truly pristine young impact structures with the most modified of the ancient structures. Younger craters of the ancient family are superimposed on older ones in impact-definitive cookie-cutter bites and are not deflected as required by endogenic conjectures. Four of the best-preserved of the pre-“pristine” circular structures are huge, with rimcrests 800–2000 km in diameter, and if indeed of impact origin, must have formed, by analogy with lunar dating, no later than 3.8 Ga. Much of the venusian plains is seen in topography to be saturated with overlapping 100–600 km circular structures, almost all of which are disregarded in conventional accounts. Several dozen larger ancient plains basins reach 2500 km in diameter, are themselves saturated with midsize impact structures, and may date back even to 4.4 Ga.”

    Of course, eventually these protracted to and fro’ risk devolving into meaningless pattern recognition. Without being able to read the paywalled away papers, the RTT evidence sounds a bit more promising.

    My layman take FWIW (i.e. not much): Extraordinary claims like catastrophic resurfacing, not seen anywhere else to my knowledge, needs extraordinary evidence. However, apparently the evidence is even less than ordinary to some. At the very least it seems like an open question?!

  24. Torbjorn Larsson OM says:

    HTML fail. It was supposed to be:

    Venus goes through periods as a complete magma planet.

  25. Paul Eaton-Jones says:

    I seem to remember an article in Scientific American [?] /Astronomy [?] or somesuch from 15 or so years ago which suggested that the bigger impact craters did date from 4GYA when the venusian atmosphere was not as thick and the paucity of later/smaller impact craters was due to the fact that as the atmosphere thickened so it stopped all but the largest asteroids/meteors getting to the surface.

Comments are closed.