Pluto

[harmonicaman]

<b>CuddlyRocket -</b><br /><br /><i>"...most astronomers want the thing settled one way or another."</i><br /><br />True; but this solution is the ultimate "Design by committee" screw up! The whole concept behind the effort to create a coherent planet definition was to make the Solar System a more logically categorized and understandable place, (a scientific process called disambiguation).<br /><br />The proposed solution just makes a huge unnecessary mess!

 

[3488]

3 Juno is irregular. <br /><br />2 Pallas is slightly out of round & rotates on its side like Uranus, asteroids 433 Eros & 511 Davida. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[alokmohan]

http://whatis.techtarget.com/definition/0,,sid9_gci874014,00.html.I AM IMPRESSED .THEY HAVE MADE IT A MESS.

 

[3488]

I agree alokmohan. It is a mess. Charon IMO is still a moon, not a planet as it orbits Pluto (although the barycentre is between the two, about 20% of the distance from Pluto to Charon). <br /><br />2003 UB313 (Xena) is a planet, as are 2005 FY, 2004 DW (Orcus), Sedna & Quaoar. If 4 Vesta is promoted than the larger 2 Pallas needs to too.<br /><br />I think that 1 Ceres was right to be promoted. It is more planetary than asteroidal IMO. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[alokmohan]

Mercury is smaller than Ganymede.Still its is planet.How?

 

[qso1]

Thanks for that image. Is that an HST or unmanned probe image? <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[mikeemmert]

That's a Hubble shot, from Wikipedia.<br /><br />There are people who post images from the Mars rovers and Cassini over on Missions and Launches. Sometimes they come here, 3488 is one of them (Voyager images). I don't know where they get the raw images from, I think they'll tell if you ask.

 

[cuddlyrocket]

"Charon IMO is still a moon, not a planet as it orbits Pluto"<br />Charon does not orbit Pluto. For an object A to orbit object B, the barycentre must be within object B.<br /><br />'Xena' is a planet. The other objects you mention are on a list of 'candidate planets' - i.e. they are objects that might be planets, but there is currently insufficient information to tell one way or the other.

 

[cuddlyrocket]

Mercury is a planet because it orbits a star (and because it is big enough for gravity to force it to be round). Ganymede is not because it doesn't orbit a star, it orbits a planet (and despite the fact that it is big enough for gravity to force it to be round).<br /><br />Size is not the only criterion. What the object is orbiting also counts.

 

[tjbaby]

Although space probes have crossed Pluto's orbit; Why have they never visited the planet?

 

[drwayne]

Crossing a planets orbit is only part of the problem. You have to do it at the right time so that the planet is "home" when you get there.<br /><br />Missions that have crossed the orbit have tended to be aimed at the large planets, and a fly-by of Pluto has not been a priority.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[CalliArcale]

There are two reasons.<br /><br />First of all, Pluto orbits outside the plane of the ecliptic, so most of the time, a space probe would have to change its orbital plane (which requires a lot of energy) to visit it.<br /><br />Secondly, only two probes (other than New Horizon) ever came close to the opportunity of visiting Pluto: the Voyagers. However, what with one thing and another, the way things ultimately worked out, it wasn't possible. They would have had to sacrifice various flyby opportunities in order to do it, and the gas giants were much higher priority targets. Basically, although they crossed Pluto's orbit (sort of; they weren't in the right plane at the time), they didn't really have any way of getting there.<br /><br />Since the grand alignment that the Voyagers exploited, there hasn't been another opportunity to visit Pluto *and* other planets besides Jupiter. Which means that a probe to Pluto is esentially a probe *only* to Pluto, which means you're going to get a lot less science back for your money. It took a long time for mission planners to convince the budgetary types that a probe to Pluto was worth the expense -- and it took the development of much cheaper spacecraft. New Horizons cost a fraction of what either of the Voyagers cost. Ultimately, they were able to slightly force the issue by pointing out that now was the last opportunity to observe Pluto's atmosphere for many generations. No one alive today will get the chance again, so it was now or never, really. Even so, it's considerably scaled back from the original plan (Pluto-Kuiper Express).<br /><br />Even so, it's going to be a very fast encounter, lasting just a few days. There's no way New Horizons could enter orbit around Pluto. It's a lot of money, and a lot of risk. But I personally feel that the scientific reward will be well worth it. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[willpittenger]

In one word? Expense. The Voyager probes were really the only ones with a chance. Unfortunately, Pluto was no where near the Grand Tour route. Since then, we have launched New Horizons. It will do a high speed flyby of Pluto and then attempt to intercept some Kuiper Belt objects. Those have yet to be concluded as we don't know what is along PKE's path.<br /><br />Why a flyby and not an orbiter? Again. Expense. In order to get to Pluto before the light failed and the atmosphere froze out, we needed PKE to reach record speeds. It is now the fastest spacecraft we have ever launched. That speed prevents the orbiter from slowing down enough for Pluto to capture the probe. Besides, this way we can checkout those KBOs.<br /><br />Pluto Kuiper Express's official homepage<br /><br />Edit: I used a name that was out of date when I searched for Wikipedia's page on the probe. Sorry. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[drwayne]

Orbit adds another complication to the problem - you have to not only be at the right place and right time for the planet's orbit, but you have to be there at a certain speed. Too fast or two slow and you don't go into orbit.<br /><br />That is one reason why probes to the inner planets take longer than you might think, judging from their difference in orbital distance.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[willpittenger]

Which is why Messenger will need so long to reach Mercury. Hopefully it will be worth it. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[MeteorWayne]

Other reasons:<br /><br />Bang for the buck.<br />Such missions are pretty expensive (even though NH is a cheap one), but back when Pluto was a planet, it was a rather dull one, by planetary stardards.<br />The gas giants are amazing, have rings and moons, from which we have learned a lot. Pluto was a lone iceball in the outer woods of the solar sytem.<br /><br />Missions could be designed to visit more than one of the outer planets in one launch. Because of Pluto's inclination, and resonant orbit with Neptune, that's not an option.<br />It requires a dedicated mission.<br /><br />Once those explorations were under way, it made sense to move on to the next targets. When missions to Pluto were being designed it was an obvious next target.<br /><br />But there's only so much money that has to be stretched out, so New Horizons Pluto mission went through some rough times.<br />But finally, the physics of the solar system made it an undeniable priority.<br />After Pluto reached perihelion, because of it's eccentric orbit it would be rapidly losing heat.<br />Once that process starts, over time the atmosphere is going to freeze out for most of the rest of it's orbit, or over 200 years before it's atmosphere comes back. That's at least the year 2200.<br /><br />So if a mission was going to go to Pluto, it had to be now (and fast) because in a few decades we would lose much of the value.<br /><br />In actuality, when we began to seriously examine Pluto's place in the solar system, starting with QB1 just over 15 years ago, we finally had proof that Pluto was a large member of tens of thousands of objects in the outer solar system.<br /><br />So it was time to take a look at this large (though as we've discovered not the largest), resonably close member of this new class of objects.<br />Plutinos, TNO's, KBO's, QBO's, Scattered disk objects.<br /><br />Yes and even the residents of the Asteroid belt, hence the upcoming Dawn mission to two of the largest asteroids, 1 Ceres, and 4 Vesta.<br /><br />Aft <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[dragon04]

Great question! And the answer has been pretty much covered. <img src="/images/icons/smile.gif" /><br /><br />The short answer is that Pluto was not in the right place at the right time for either the Pioneer or Voyager missions to fly by and do what their missions wanted to do.<br /><br />In addition, compared to the 8 planets that circle the Sun, Pluto's orbit is "inclined" or "declined" to th ecliptic. That adds another problem.<br /><br />Imagine our solar system as a plate. Imagine the 8 planets as little balls travelling around flat on that plate at varying distances.<br /><br />They really don't exactly, but for our purposes, we can say that they do.<br /><br />Now for Pluto. It's off the edge of the plate. Not only that, but it's only level with that plate for a small amount of time twice every 248 years or so. MOst of the time, it's above or below the plate.<br /><br />The short answer is what I said first. It just wasn't in the right place at the right time. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[vogon13]

An early mission concept for Voyager had spacecraft flying the Earth - Jupiter - Uranus - Neptune trajectory and an Earth - Jupiter - Saturn - Pluto trajectory.<br /><br />Getting funding from the US Congrees was the problem as the science goals were pretty vague in those days.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[willpittenger]

Please describe how you could put a probe in orbit around Pluto. You can have your probe leaving or being built in the past -- as long as you limit the technology and booster to what was available then.<br /><br />Please state each of the following:<ol type="1"><li>Choice of launch vehicle and booster<li>What instruments would be present<li>When it would leave<li>What flybys you would need to make to reach and orbit Pluto<li>How long your mission would need to reach Pluto<li>How heavy you think the probe would be<li>How long you think your probe would survive in orbit around Pluto<li>Full reactor or a RTG?</li></li></li></li></li></li></li></li></ol><br /><br />BTW: Your mission might actually fly -- not to Pluto but to something in a similar orbit. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[vogon13]

Looks like ballute technology will put just about anything except a manned craft in orbit around Pluto.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[willpittenger]

No details? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[mithridates]

Rover on Ceres! Rover on Ceres! A jumping one, since the gravity is so low. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[MeteorWayne]

How would a ballute help?<br />Pluto's atmosphere is exceedingly thin, not enough there for aerobraking of any kind.<br />And for most of it's orbit, once the gases freeze out, there's even less.. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vogon13]

As it turns out, due to the low gravity of Pluto, the atmosphere (when available if it turns out to be variable) billows up to great height.<br /><br />Decels up to 40 Gs seem attainable (hence technique not being suitable for people) and the ballute can 'bank' during decel (like the Space Shuttle) to align with more favorable targets.<br /><br />Possible to put a lander just about any where you want on Pluto, or to head on to flyby Charon or Nix or Hydra. <br /><br />The ballute would also work at Triton for orbit insertion around either Triton or Neptune. Consider most of the velocity dissipation during re-entry at earth occurs over 50 miles up, and then realize the atmospheric density of all these atmosphered bodies under discussion here is similar at some altitude. Ballute is sized to a range of expected decel parameters and delivered mass to target.<br /><br />It turns out navigation during the decel isn't that hard either. Monitor change in velocity and heading and then cut the cord to the ballute when you are in the 'green' area on your arrival graph. Having an orbiter and lander in tandem is possible too. Cut loose orbiter to orbit target, and leave lander attached to ballute to ride it all the way down to the surface.<br /><br />Utility of the technique is amazing and compelling.<br /><br />(this ballute thingy isn't one of my ideas, someone at JPL came up with it)<br /><br />(steering it might be, though) <br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[MeteorWayne]

Sorry, I just have a hard time believing that Pluto's atmosphere is thick enough to give 40 g's of deceleration.<br /><br />Let me look up some numbers, unless you have on site measurements <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>