Category Archives: Space Exploration

Jupiter Science from Juno Coming Out

The Juno spacecraft has been in orbit around Jupiter since July 2016, and will complete at least two more orbits under current funding (July, 2018).

One of the goals of the mission is to look in detail at the atmosphere of this gas giant.  From Earth, we can see the stripes, which are vast wind streams (in opposite directions ?!), and the Great Red Spot, the largest hurricane in the solar system. But what is going on under the cloud tops?

After more than a year of data collection, results are starting to come in.  Jonathan Fortney summarizes three new papers appearing this spring in Nature [2].  Fortney points out that Earth bound experiments and  theory have not been able to describe the complicated Hydrogen / Helium atmosphere below the surface we can see.

One study investigated the mass distribution of Jupiter by measuring the Doppler effects on the radio signals from the Juno spacecraft as it swooped past [4].  Fortney notes that this was a very finicky process, which had to account for tiny amounts of acceleration including the absorption and re-radiation of sunlight!  The researchers conclude that the bands we see extend quite deep into the atmosphere.

A second study extends this work to conclude that the strong winds decay slowly down some 3.000 kilometers [5].  I.e., the bands we see probably extend down some 3,000 kilometers into the atmosphere.

A third study finds that below that depth, the planet rotates as a solid [3]. At that depth, the pressure is such that the hydrogen ionizes and electromagnetic forces bind the material into a liquid. (This core is the source of the strong magnetic field.)  Obviously, there must be a very turbulent area at the boundary of these two regions, with huge bands of wind ripping East and West across an inner core.

These studies give a picture of a dense interior, with a deep atmosphere dominated by huge bands of strong winds.  An extremely stormy planet!

See swirling cloud formations in the northern area of Jupiter’s north temperate belt in this new view taken by NASA’s Juno spacecraft. The color-enhanced image was taken on Feb. 7 at 5:42 a.m. PST (8:42 a.m. EST), as Juno performed its eleventh close flyby of Jupiter. At the time the image was taken, the spacecraft was about 5,086 miles (8,186 kilometers) from the tops of the clouds of the planet at a latitude of 39.9 degrees. Citizen scientist Kevin M. Gill processed this image using data from the JunoCam imager.

(Caveat:  these studies are based on the theory of gravitational harmonics which I don’t understand at all.)

Fortney suggests that Juno may be able to make further detailed observations of the Red Spot and other storms, which would be interesting details to have.  He also notes that data returned by the Cassini probe of Saturn should yield comparative measurements for the its less dense and probably deeper atmosphere.

Stay tuned. There is lots of other science coming.

The current funding ends in July, but the mission could continue for several more years if supported.


  1. Jonathan Amos, Jupiter’s winds run deep into the planet, in BBC News – Science & Environment. 2018. http://www.bbc.com/news/science-environment-43317566
  2. Jonathan Fortney, A deeper look at Jupiter. Nature, 555:168-169, March 7 2018. https://www.nature.com/articles/d41586-018-02612-y
  3. T. Guillot, Y. Miguel, B. Militzer, W. B. Hubbard, Y. Kaspi, E. Galanti, H. Cao, R. Helled, S. M. Wahl, L. Iess, W. M. Folkner, D. J. Stevenson, J. I. Lunine, D. R. Reese, A. Biekman, M. Parisi, D. Durante, J. E. P. Connerney, S. M. Levin, and S. J. Bolton, A suppression of differential rotation in Jupiter’s deep interior. Nature, 555:227, 03/07/online 2018. http://dx.doi.org/10.1038/nature25775
  4. L. Iess, W. M. Folkner, D. Durante, M. Parisi, Y. Kaspi, E. Galanti, T. Guillot, W. B. Hubbard, D. J. Stevenson, J. D. Anderson, D. R. Buccino, L. Gomez Casajus, A. Milani, R. Park, P. Racioppa, D. Serra, P. Tortora, M. Zannoni, H. Cao, R. Helled, J. I. Lunine, Y. Miguel, B. Militzer, S. Wahl, J. E. P. Connerney, S. M. Levin, and S. J. Bolton, Measurement of Jupiter’s asymmetric gravity field. Nature, 555:220, 03/07/online 2018. http://dx.doi.org/10.1038/nature25776
  5. Y. Kaspi, E. Galanti, W. B. Hubbard, D. J. Stevenson, S. J. Bolton, L. Iess, T. Guillot, J. Bloxham, J. E. P. Connerney, H. Cao, D. Durante, W. M. Folkner, R. Helled, A. P. Ingersoll, S. M. Levin, J. I. Lunine, Y. Miguel, B. Militzer, M. Parisi, and S. M. Wahl, Jupiter’s atmospheric jet streams extend thousands of kilometres deep. Nature, 555:223, 03/07/online 2018. http://dx.doi.org/10.1038/nature25793

 

Space Saturday

 

Life On Ocean Worlds

One of the great philosophical mysteries of our age is, in the words ascribed to Enrico Fermi (AKA, “the pope of physics”): “Where is Everybody?” [3]  (This is known as Fermi’s Paradox, though he didn’t originate it, nor is it really a ‘paradox’.  It’s still a Fermi-grade question, though.)

Humans have been watching the skies for millennia, and in the past century have looked ever wider and deeper into the universe, not to mention into physics and the biology. Everything we know indicates that there could very well be life and even technological civilizations everywhere in the vast universe.  But we have never seen evidence of life beyond Earth.

Where is everybody?

Coming up with answers to Fermi’s question is a great scientific parlor game.

In 2002, Stephen Webb describes 50 answers [2], and in his 2015 update he gives 75 (!) [3].  The “solutions” listed by Webb range from “they are already here”, through “they are so strange we don’t recognize that they are there”, as well as the possibility that life really is very, very rare.

Along the way, he points out many uncertainties in our estimates of how likely the development of life and “intelligent” life may be (e.g., we have only our own planet to extrapolate from), as well as unknowable hypotheses about the possible psychology or politics of putative non-human civilizations (e.g., just because we want to talk to everyone doesn’t mean anyone wants to talk to us).

There are also disturbing warnings that “civilizations” are likely to self-destruct before escaping their home planet, or, even worse, may be snuffed out in the nest by predators or catastrophes. (With this in mind, blasting our electromagnetic presence in all directions might not have been a healthy life style choice.)

Webb’s compendium of “solutions” is fun to read, but the game is hardly over.


At the 2017 Habitable Worlds workshop, S. Alan Stern proposes yet another solution to the Fermi Paradox: most life evolves in “interior water ocean worlds”, i.e., in oceans under thick ice covers [1].

most life, and most intelligent life in the universe inhabits interior water ocean worlds (WOWs) where their presence is cloaked by massive overlying burdens of rock or ice between their abode and the universe.

There are several such worlds in our own solar system, and at times in the past the Earth itself flirted with such conditions, covered over with a kilometer of ice.

Artist’s concept of Europa’s frozen surface. Credit: JPL-Caltech

Stern notes that these worlds appear to be highly conducive to the development of life.  The ice cap protects and stabilizes the ocean environment, providing a nest for fragile life to develop over long, evolutionary periods of time.  Thus, however likely life is to develop, ice worlds are prime candidates for successful evolution.

However, Stern also makes the interesting inference that life that evolved under a deep ice cap would have no direct view of the universe.  The protective shield overhead would also block out most evidence of other stars and planets. An emerging civilization under the ice would not know about the universe, at least until technology develops that detects (indirectly) the space above the ice.  Even then, intelligent beings might have difficulty imagining life that does not live under ice, so they might not think to look for signals from us or send signals we could detect.

Stern also argues that life adapted to an ice-covered ocean would find space travel difficult, at least compared to species adapted to the surface under a gaseous atmosphere. In addition to the technical challenge of penetrating many kilometers of rock hard ice, life-support would be necessary to support a dense, liquid environment.

He combines these arguments to answer the “Where is everybody?” question:  if much life develops in ice covered oceans, and any civilizations in such environments unlikely to know or care about the wider universe, then this explains why we haven’t heard from them.

This is an interesting idea to think about.  It is certainly useful to break out of the parochial idea that an Earthlike planet is the only or ideal locus for life or “civilization”.  In fact, we know that life on Earth has just barely survived at least five major extinction events, and an ice world might well be a safer crèche.

I’ll also note that his comment that life on such a planet “either cannot communicate or are simply not aware that other worlds exist” works both ways.  It is difficult for us to detect such inhabitants, and we haven’t be looking until recently.  In our own solar system, there are several ice worlds, but we still have no idea if they are inhabited or not.


On the other hand, several aspects of Stern’s argument are less convincing to me.

An ice-covered ocean world might be a favorable site for life to start, but it might also be a closed system that is quickly exhausted.  Experience on Earth certainly indicates that a closed “ark” will rapidly be overgrown, clogged, and die out.   It is likely that only some ice worlds will be sufficiently “active” or open enough for life to persist.  But who knows until we actually check.

I have to say that I find the arguments about the supposed psychology of native to ice worlds highly speculative, to say the least.  It is true that life on Earth can directly sense the solar system and wider universe, and there are plausible arguments that this knowledge has strongly influenced the development of what we call intelligence.  But it is very difficult to guess the implications of not having an open sky.

I also think that, should a technological civilization develop under an icecap, it will surely develop undertanding of the outside universe. They’ll surely learn about gravity, and when they learn to detect and manipulate electromagnetism, they’ll soon notice a lot of interesting stuff coming in through their icy roof.  For that matter, no matter how difficult space travel might be, wouldn’t they deploy robot explorers and harvesters on the outer side of the ice.  And from that perch, who would not look up and see other worlds?

In short, I’ll buy the idea that ice worlds are good places for life to develop, though they may not be great places to sustain life for billions of years.  But I reserve judgement on questions of how the lack of a sky might influence the development of “civilizations”.


In this article, Stern describes yet one more case for why there could be some extraterrestrial civilizations that we have not seen or heard.  But this clearly isn’t “the answer”. He joins the roster of all the dozens of other hypotheses (Indeed, Webb has a solution called “Cloudy Skies Are Common” ([3], p. 183), which probably subsumes Stern’s solution as a sub case.).

On the other hand, this thesis is yet more reason why icy ocean worlds are really interesting and really need to be explored..  There very well could be life under the ice, and we really should find out what we can.

We have several such worlds close at hand in our solar system that we could visit and actually see what is down under the ice. (EuropaEceladus!  Titan!)

Let’s go, already!


  1. S. Alan Stern, An Answer to Fermi’s Paradox in the Prevalence of Ocean Worlds?, in Habitable Worlds 2017: A System Science Workshop. 2017: Laramie, Wyoming. https://www.hou.usra.edu/meetings/habitableworlds2017/pdf/4006.pdf
  2. Stephen Webb, If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, New York, Copernicus Books In Association With Praxis Pub, 2002.
  3. Stephen Webb, If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY? Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, New York, Springer, 2015.

 

Space Saturday

Cassini End of Mission

After twenty years in space (launched 10 years Bi, Before iPhone), traveling over a billion KM, and returning data for 13 years from more than a light-hour from Earth, the Cassini Spacecraft ended its mission this week.

The project has accomplished lots of amazing science, represented by 3,948 papers so far. There will surely be a few more—lets go for 5K papers!

The end was a planned dive into the atmosphere of Saturn, collecting a few more bits of data on the way down, and assuring the complete destruction of the spacecraft.

As has been explained before, the spacecraft needed to be vaporized to prevent even the slighted chance that it might contaminate the area with Earth microbes. Aside from not wanting to harm any life that might exist on the moons or dust, we also don’t want to accidentally leave something that a later spacecraft might find and not realize was inadvertently sent from Earth.

(Which, if you think about it is way, way cool. How many human endeavors have to worry about the possibility of contaminating alien ecosystems, even in principle?)

Hence, the final dive.

This montage of images, made from data obtained by Cassini’s visual and infrared mapping spectrometer, shows the location on Saturn where the NASA spacecraft entered Saturn’s atmosphere on Sept. 15, 2017. Credit NASA/JPL-Caltech/Space Science Institute

Cassini signed off permanently on September 15. Loss of Signal. End of Mission. Lots of accomplishments.

 

Space Saturday

Interplanetary Networking

Space travel faces inevitable communication challenges. Even within the solar system, distances are light minutes to hours, which means round trip latencies that preclude easy conversation. In addition, signals decay quadradically, so there is a brutal power-to-distance relationship—and power is precious in space.

Can we do better than radio signals?

Gregory Mone reports in CACM that the answer is, lasers, man! [2]

Lasers are higher frequency and narrower beams, so they can transmit more data for the same power. This can’t eliminate the latency, but can push more data in a given time. As much as 10-100 times the data, which is worth a lot of effort to make happen.

A laser is much more directional than radio, and the receiver is a telescope. The narrow beam is a challenge, because the signal has to be aimed precisely. Given than everything is moving rapidly relative to everything else, it isn’t trivial to keep a signaling laser pointed at a very distant target.

If you were to aim a beam of radio waves back at Earth from Mars, the beam would spread out so much that the footprint would be much larger than the size of our planet. “If you did the same thing with a laser,” Biswas  [of NASA JPL] says, “the beam footprint would be about the size of California.”” ([2], p. 18)

Experiments have demonstrated space laser communication, utilizing error correcting codes (to mitigate lost signals) and advanced nanoactuators to precisely aim the laser. At very large distances, power will be at a premium, so there will be no bits to spare for error correction.

The receivers are essentially telescopes, which are a very well known technology. Receiving weaker signals from farther away means bigger telescopes. Mone says that signals from the solar system need a 10-15 meter scope.

These links will still have extremely long latencies compared to terrestrial networks. This means that our Earth bound protocols need to be redesigned for the Interplanetary Internet. (Hint: timeouts don’t work well if the round trip time for an ACK is variable and measured in hours.) This work is well underway [1].

Cool!

  1. InterPlanetary Networking Special Interest Group (IPNSIG). InterPlanetary Networking Special Interest Group (IPNSIG). 2017, http://ipnsig.org/.
  2. Gregory Mone, Broadband to Mars. Commun. ACM, 60 (9):16-17, 2017. https://cacm.acm.org/magazines/2017/9/220434-broadband-to-mars/fulltext

 

Remote Fun Park On The Moon?

As we approach the fiftieth anniversary of the first moon landing, it is clear that humans have pulled back from space exploration and from science in general. NASA’s budget has steadily declined, dedicated scientists politically suppressed and much of the space program has calcified into a jobs program.

What can be done?

Toys! Theme parks!

There is a lot of interest these days in sending swarms of small robots to the moon. Perhaps inspired by ubiquitous remote piloted drones, why not remote operate a moon rover?  And why can’t anybody drive one, with a game controller?

The Lunatix company is proposing to sell moon-rover-driving as a game. Earth bound computer games would be linked to the lander, and could purchase driving time. Kind of like consumer drones, except on the moon [3].

The lander might have a small science payload, but mainly it is dedicated to the commercial use. (There would be merchandise and other associated sales, as well.)

This seems relatively straightforward technically. There are some tricky bits, such as linking a consumer via the Internet to an uplink to the moon. Safely linking. Securely linking. (Hint: space communications are expensive and rare, and generally not connected to the public.)

I have no idea about the commercial case. Space projects are obscenely expensive, but getting cheaper. At something like 25 Euros per minute, it seems to me that driving time would be pretty damn expensive, at least for peasants like me. But who knows? My intuitions about business plans are often wrong.

Evan Ackerman points out that this purely commercial project raises legal questions. The moon is more or less under the jurisdiction of the United Nations, as defined by treaties among nations. There seems to be no specific framework for commercial exploitation of the moon, though there will surely need to be one soon.

Aside from the equity issues about sucking money out of the lunar commons (the moon is the common heritage of all human kind), there may be environmental and other regulatory issues.

I note that a company slogan is “Leave Your Mark on the Moon!”  The users will leave behind tracks, indelible tracks, visible from Earth.  This will surely have consequences.

How happy are we going to be when the moon is covered with tread marks? Do you want to see rude graffiti defacing the surface? How will we feel about a giant cola ad written in the dust? How will Earthly strongmen react to uncensored political messages, indelibly written on the moon?

The company proposal seems to wave its hands at the legal problems and doesn’t even list any legal issues under “Risks”. That may be optimistic.

In the end, it is quite possible that money will talk. As Ackerman puts it, despite his own misgivings, “If this is the best way to get robots to the moon, then so be it”.

While there’s a small section in the Lunatix executive summary on “Legal Framework,” there are few specifics about whether or not the United Nations would approve something like this. Lunatix seems to suggest that its use case is covered under “the common interest of all mankind in the progress of the exploration and use of outer space for peaceful purposes,” but I’m not so sure. It may be that no framework exists yet (either for or against), and my gut reaction that commercializing the moon in this way somehow cheapens it is probably just me being old and grumpy. If this is the best way to get robots to the moon, then so be it.” (From Ackerman [1])

I have my doubts about this concept. We’ll see.

But the general idea that some kind of entertainment business might be one of the earliest commercial successes for space seems to be plausible. Many important technologies started out as entertainment, or were driven by markets for entertainment [2].

For example, the Internet was designed for military and scientific applications, but the earliest commercial successes were music theft, games, and pornography, which drove markets for servers, GPUs and broadband, among other things. Today’s cord cutters are simply taking advantage of the second and third generation of these technologies. And, just as the Internet has never been comfortable with the fact that it is a great mechanism for delivering pornography, space entertainment may not turn out quite as imagined.

 


  1. Evan Ackerman, How Much Would You Pay to Drive a Jumping Robot on the Moon?, in IEEE Spectrum – Automation. 2017. http://spectrum.ieee.org/automaton/robotics/space-robots/how-much-would-you-pay-to-drive-a-jumping-robot-on-the-moon
  2. Steven Johnson, Wonderland: How Play Made the Modern World, New York, Riverhead Books, 2016.
  3. Space Tech, Luniatix. Graz University of Technology Institute of Communication Networks and Satellite Communications, 2017. https://www.tugraz.at/fileadmin/user_upload/tugrazInternal/Studium/Studienangebot/Universitaere_Weiterbildung/SpaceTech/Fallstudienprojekt_ST14.pdf

 

 

Space Saturday

Happy Anniversary Voyager I and II

Forty years in space and billions of kms out, and still going!  Over half a light-day out, and heading for the stars.

As they say, “The Interstellar Mission”.

A few years ago, I asked a friend of mine, who was and is ON ONE OF THE VOYAGER SCIENCE TEAMS (we are not worthy! we are not worthy!), what’s up with the Voyagers?

He told me that the signal is getting weaker, but antennas are getting a lot better—so they still get a trickle of data back.

The don’t make ‘em like they used to!

Well done all.

 

Space Saturday

Grand Finale And A New Target

In the next weeks Cassini enters its final 5 orbits, swooping lower and lower, flying inside the rings of Saturn, until the final plunge on September 15, the “Grand Finale”.

At the same time, the New Horizons probe screamed past Pluto two years ago, but it has no brakes so it is still going out into the Kuiper Belt, which is cold, far away, and gigantic. The probe is still alive, though slumbering.   But with luck, it will wake up in 2019 and take some pix of Kuiper Belt object (KBO) 2014 MU69. This will be up close images 6 billion KM from home.

You can tell this is a long way out, because New Horizons is now half way between Pluto and the second stop on the itinerary.  This second leg is four years to complete.

This cunning plan got even more interesting this week, with reports from an occultation study in July that suggests that 2014 MU68 is not a ball. It may be an odd shaped blob or even two objects close together.

Whatever MUey-69 looks like, New Horizons may be able to get a good look.   Cool.


  1. Cassini Science Communications Team. The Grand Finale Toolkit 2017, https://saturn.jpl.nasa.gov/mission/grand-finale/grand-finale-orbit-guide/.
  2. Bill Keeter. New Horizons’ Next Target Just Got a Lot More Interesting. 2017, https://www.nasa.gov/feature/new-horizons-next-target-just-got-a-lot-more-interesting.

 

 

Space Saturday

PS.  Yet more names for bands:

Final Five Orbits
Kuiper Belt & Braces
A Belt of Kuiper
The Grand Finale Toolkit