Wednesday, 16 September 2015

"We are trained not to jump to conclusions." - a conversation with Carolyn Porco

Carolyn Porco is the go to person when it comes to planetary rings and the small active moon, Enceladus. For the past 25 years she led Cassini imaging team, which brought us some of most spectacular space pictures in the history. She also was part of Voyager mission and New Horizons mission (among other scientific activities).

She concieved the idea of taking the famous “The Day the Earth Smiled” photo. She was on TIME magazine list “The 25 Most Influential People in Space”, on "The 50 People Who Matter Today" list by New Statesman magazine, and on “Wired magazine's first-ever Smart List” Wired magazine.

She also says we should have annual parades celebrating landing on Titan, and I couldn’t agree with her more. In short - she’s awesome and she found time to talk to me.

It seems like the past 12 months were like continuous christmas. We’ve landed on a comet, we’ve entered Ceres’ orbit, and swooshed right by Pluto. How and how soon can we top that? What do you think should be the next big thing or things?

These were all ‘firsts’, and we do love ‘firsts’, don’t we? But they were all relatively small missions. We could top that by doing either or both of the following.

Finally, put a Cassini-class orbiter in orbit around the planet Neptune. Here is a planet that Voyager visited 26 years ago, and it is actually a fascinating planetary system, hosted by a body that is not like Jupiter or Saturn, but different in important regards. And it has, of course, Triton … the ‘cousin’ to Pluto. We only flew by this place, and we need to study it in the way we’ve studied Saturn and its system. An orbiter is clearly the way to do it and would be the only ‘next step’ that could provide a quantum leap over what we found with Voyager.

Send a spacecraft to Enceladus to address one and only one question: Do its geysers, which are sourced in a salty, organics-laden ocean far beneath the surface, contain evidence of life? THAT could be the mission that returns the Holy Grail.

New Horizons will be sending us data for quite some some time, but what would you say is the biggest surprise New Horizons has shown us so far?

The complexity of the Pluto surface is far and away the best and biggest discovery. I can’t say it was totally unexpected: We developed our expectations based on what Voyager found at Triton: a very complex, varied, extensively worked surface, with active plumes reaching 8 km skyward. So, we – or at least, I – expected to see an equivalent level of complexity. But no matter how much you anticipate one thing or another, it’s always a ‘surprise’ when you finally see it because it’s not exactly what you thought. It’s always a variation on a theme.

In Pluto’s case, we expected to see geology born of the process of sublimation and condensation of volatiles. But did anyone expect that there would be a very large but clearly defined region, made of volatiles and seemingly thick enough to flow, showing signs of long-time-scale solid convection (if in fact that theory is correct)? Not at all!

The Pluto images are simply dazzling, and I’m always struck, during these events, at how limited our imaginations were in predicting what would be there. It’s not a failure of thought; it’s more often a failure of imagination that brings about the surprises.

I wonder - can Pluto encounter impact the way we see or study the inner solar system? For example could it somehow impact Cassini mission?

No. First, the Cassini mission is nearly over… just 2 more years to go… and our plans are solidified, with very clear goals. That won’t change. And the two systems are very different: Pluto, remember is tiny, less than half as big as Titan. It’s like a mid-size Saturnian moon (smaller than our moon) at the edge of the solar system. Second, the inner solar system is even more different than Pluto than the Saturnian system is. Remember, it is very, very cold out there. And so the active, volatile materials you’re seeing on the surface of Pluto are very different than the ones we see in the inner solar system. Two entirely different physical realms.

The real scientific significance of the Pluto flyby is that it has shown us what an object in the Kuiper Belt, one that has been more or less left unaltered for billions of year, looks like. We’re looking at processes that no doubt are ancient and have been left to play out for the age of the solar system (or close enough). That is why this flyby has been so thrilling. It’s like visiting the solar system back in the really old days.

For more than a decade Cassini has been giving us georgeous pictures of Saturn and its system. What can we expect in its final years?

More of the same! And hopefully answers to some questions that we’ve long had, like “How massive are the rings?” And “what are the processes that occur in the auroral region on Saturn?” And “Is anywhere else on the south polar terrain of Enceladus warm besides the 4 main fractures?” And “Does Enceladus’ plume vary on long timescales?”

Speaking of Saturn system and Titan… While it seems as different from Earth as it gets (it is a cold moon of a gas giant with methane-rich atmosphere), it also seems eerily similar. Does it mean that if there are Earth-like planets with bodies of water out there, they are going to look very much like our pale blue dot?

If they are rocky and they have water and conditions at the surface are the same, chances are good they will have very similar surface- and atmosphere-altering processes. Therefore, they are likely to look similar: That is, similar landforms. This is what is ‘similar’ about Titan too. What is dissimilar on Titan are the materials: instead of silicate rocks, the ‘hard surface’ is water ice. Instead of water, it’s methane. Like science fiction!

Could you compare Europa and Enceladus in terms of how interesting each one is, or which one you think should be explored first?

I lost this argument. My stance was simple: If the goal is really to find an extraterrestrial habitable zone that could support life and go investigate it, Enceladus was the best find in all the solar system. Its habitable zone is gushing into space and is there for the sampling. Easy sampling too: you don’t have to land, scratch the surface, or dig, or even bunker your spacecraft in lead to protect it from intense radiation. It’s extremely straightforward: make sure your spacecraft is properly equipped and fly through the plume collecting samples.

And we know so much more about Enceladus than we do about Europa, because Galileo had a broken antenna and we didn’t even get to image the entire surface! In contrast, we’ve spent the last 11 years studying Enceladus and we have a very deep level of knowledge on it and its activity.

So all other things being equal, Enceladus was the clear winner.

Europa, however, had a huge ‘following’, as it were, because people had been promoting a mission to Europa for many years, when it was the best astrobiological target around. Well, Enceladus trumped it in the astrobiology arena but the political momentum behind Europa was unstoppable and what carried it to ‘new start’ status.

Now mind you: There are plenty of reasons to study Europa. It obviously has had a fascinating geological and geophysical history, and there is much yet to discover that Galileo couldn’t. So there will be much to learn and it will be a thrilling mission for sure. But what the next Europa mission will largely do is bring our knowledge of that moon up to the level we have on Enceladus today. And only after that point will we be in a position to judge how easy or not it will be to access its ocean.

For now, the operative word in support of Enceladus is ‘Accessibility’!

Most scientists try to be very careful with making extraordinary claims. What extraordinary kind of data or observation would be conclusive enough to announce that we’ve found life on Mars, Europa/Enceladus or on an exoplanet?

When we can hold an alien life form – being it macroscopic of microscopic – in our hand, without all the qualifying conditions that remote sensing of a body requires. Doing that may necessitate bringing samples back to our Earth-based laboratories. But then we’d be in the best situation possible to judge. Until then, we’ll be attaching levels of confidence to our observations. You might find us saying things like, ‘Our instruments have determined that there is a level of chirality in this sample of Enceladus’ plume that is very unlikely to be from anything other than biology’. But there will always be a nagging doubt. Scientists, as you point out, are a conservative bunch. We are trained not to jump to conclusions.

Let’s say there IS life on each. Underground on Mars, in the ocean of one of icy moons, and widespread on one of transiting Earth-like planets. Where would you expect we would discover it first?

If there really is life in each location, AND we mount programs to go after such information, then Enceladus wins because (at least right now) its zone of possibility is the most accessible.

Finding life on exoplanets and being confident that it really is life is going to be extremely challenging. I’m guessing it will mostly be by inference that we make such a discovery, as in, “This exoplanet has the same size, distance from its host star, and surface composition as the Earth, we find oxygen out of equilibrium, and so we conclude …. it likely hosts life”. BUT … we won’t know for sure, and also, we are a long way away from being able to make sure measurements.

Recently you were involved with the movie Star Trek, can you say something about your input?

The director J.J. Abrams posed the question to me: ‘We have a problem. We have the Enterprise returning to the solar system to save the Earth, and we have to figure out where to hide it from the enemy? What should we do?” It seemed silly to me and I actually thought that this was a test to see if I could come up with any good ideas. But I answered, ‘Why don’t you have it come out of warp drive in the atmosphere of Titan, and rise up through the haze, submarine style?” I knew it could be made into a very dramatic scene.

To my delight and astonishment, Abrams thought the idea was 'brilliant' and immediately used it. It can be found here.

I was expecting to be asked at some point how to get around the obvious problem that any respectable starship, Federation or Romulan, would have no trouble picking up the presence of an alien ship by other than visual means, but I never was. I didn't realize until seeing the final result for the first time myself in the movie theater that they imagined it could be made invisible by the magnetic field of Saturn's rings. Of course, the rings don't have a magnetic field, and even Saturn's is not very strong -- certainly not as strong as Jupiter's -- and I would gladly have informed them of such had I known.

As you might suspect I’m sort of a big fas of Carl Sagan… I think it’s quite clear that he had a huge influence on the general public. I’d like to know what his influence was on people who knew him personally?

His colleagues who were his age resented him terribly. I’d say he wasn’t treated very well, and yet I never saw him retaliate. He was always very gracious and patient, even when publicly ridiculed.

But people my generation and younger loved him. He was the coolest, most gracious, non-judgmental, respectful, kind person imaginable. And very old world. I half expected, when he greeted me (sometimes even kissing my hand), that he’d also bow.

Speaking personally, it’s hard for me to describe the effect that Carl had on me. When I find myself in a particularly uncomfortable or stressful professional situation, I often think, “How would Carl handle this?” Our community lost a great deal the day he passed away. He was a truly special individual and I miss him very much.

Thank you for your time.

Thank you!


Sunday, 10 May 2015

Could Ultron's plan work?

Fellow blogger Bobrownia gave me the idea for this entry. He asked if Ultron’s plan for humanity extinction was plausible from scientific standpoint. Obviously this means a spoiler for Avengers: Age of Ultron. So if you haven’t seen it just yet, you’ll have one surprise less, but I assure you the movie has more in store.

Spoiler in 3… 2… 1…

So the question is - can you wipe out humanity by dropping something very big from very high? Simple answer is - yes. Obviously, the devil is in details. Asteroids and comets typically go at great speeds - tens of kilometers per second. Ultron had no way to send his projectile that fast, so he had to go for mass, which is inconvenient since kinetic energy is ½ * m * V2, so you need a lot more mass to make up for velocity.

To play with numbers, we’ll need some assumptions based on what we saw. The “meteor” is roughly a half-sphere. The city above is negligible - buildings may seem large, but it’s mostly empty space, incomparably lighter than solid rock or dirt. To estimate mass we’ll use density of granite. Cubic meter of dirt is around 1760 kg; let’s assume Ultron picked a rocky spot, so cubic meter will be 2600 kg. If we assume that the lifted piece was 10km in diameter (I guess it’s way more than what we saw in a movie), then it’ll weigh 700 billion tonnes.

Ultron wasn’t stupid, he knew just dropping the rock wouldn’t do the job. So he installed engines to plunge it into ground faster. Given how Iron Man got squeezed to the bottom of the “meteor”, let’s assume it’s accelerates like top Formula 1 cars, less than 20 m/s2. The biggest unknown is how high he raised the city. Let’s make another “optimistic” assumption and say it was 50 km. Arbitrary boundary of space is 100 km. The highest planes go (well Blackbird SR-71) is 26 km (85 000 feet). Actually even at the altitude of just few kilometers it gets hard to breathe, but let’s turn a blind eye to this.

So… With 50 km to gather speed, Ultron’s meteor would smack the planet releasing 700 billion gigajoules of energy - that’s 150 thousand megatons of TNT. It’s the force three thousand times that of the most powerful nuclear weapon ever detonated - the Tsar Bomba. But if we compare that to the asteroid that wiped the dinosaurs, it turns out to be thousand times weaker. To match it, Ultron would need enough time to lift the city closer to 500 km; that’s higher than orbit of ISS.

So what if the energy is smaller? A big issue for the genocidal robot is that the impact point was deep inside the continent. Dropping his “meteor” near the coast, preferably close to a tectonically active area could result in an earthquake or at least a devastating tsunami increasing the damage. Still, the calculated energy should suffice to demolish most of Europe and cause a nuclear winter in which army of robots could systematically eradicate the remains of humanity.

Carbon Chauvinist has it’s fanpage, just in case you wanna follow it.