MSL's cruise phase took place as the Sun was ramping up to an activity peak in its 11-year cycle. And as I recall, we've seen a somewhat unusually active ramp-up this time around. Perhaps radiation-sensitive payloads may have to take advantage of transfer orbit windows that occur during quiet sun periods?

-the other Doug

Yep -- a comet's apparent brightness (and especially daytime visibility) is very dependent on a lot of factors, many of them atmospheric.

The only comet I ever recall seeing in a pretty bright daytime sky was Hale-Bopp. Ikeya-Seki in 1965 was not visible in the northern hemisphere before it broke up at perihelion, so I never managed to catch it. But I do recall seeing Hale-Bopp before sunset (both from here in Minnesota and also from England, where I visited in April of '97). Only a bit of a stub of a tail was visible in daytime, but the coma was brighter than Venus usually gets at its brightest.

Of course, the most striking memory I have (and will ever have) of a comet was Hale-Bopp from the airliner I took to England. It was nighttime along the arctic great-circle route, Hale-Bopp rising above the curtains of the aurora borealis, the tail appearing first like a ghostly spotlight rising straight up out of the aurorae. In contrast to the pink of the aurorae, the tail looked almost greenish-bluish.

It's one of my most cherished memories. I do hope we get another great comet in my lifetime.

-the other Doug

Yep.

-the other Doug

Yes, they zeroed the nav system several times during the EVAs. And the system only told you the range and bearing back to the LM. Total odometry was calculable from this (it was calculated on wheel turns), but was considered somewhat of a "dead reckoning" system. Wheel slippage and meander to avoid rocks and craters meant that the nav system would get you back to where you could see the LM and drive back to it by eye. No one ever pretended that it could tell you within a few meters *exactly* where you were or how far you had driven.

On the LRV, the range and bearing were more often used in finding the planned station stops, and due to the various small detours and wheel slips these readings usually varied from the pre-mission calculated values, even when the slight variations in landing point were taken into account.

All this is to say that you'd have to do the kind of detailed wheel-track analysis they're now doing with the Lunakhods to get the absolute exact distance traveled by any of the LRVs. There is a "wander factor" in the LRV nav data that makes all calculations based on them somewhat approximate.

-the other Doug

You know, when we first got to Yellowknife Bay, I mentioned that it looked to me like some of the rocks had concretions in them, and Phil (our mapmaker for MSL). whom I much admire, replied with "Concretions, Doug? Really?" Suggesting I was seeing things that weren't there.

Nice to have heard Grotzinger later identified what I was seeing as concretions....

That said, of course, not every little round pebble on Mars is a concretion, and I totally understand caution in making identifications at first glance.

-the other Doug

Kepler did prove that the concept works. We can detect planets via the transit method. Now that the concept is proven, follow-up spacecraft can be designed to reduce the noise level even further and begin the systematic process of "mapping" local planetary systems.

While the mission tag-line, "finding new Earths," is what grabs the popular interest (and helps in obtaining funding), I'm a firm believer that it's just as important to find and categorize all of the planetary systems around us as it is to find "new Earths." After all, it's not like we have the propulsion technology to *reach* any exoplanets any time soon, so finding the planets that are there, colonizable or not, is providing a lot of basic data that we'll need if we're ever to truly understand how planetary systems are formed. (I mean, who would have guessed that binary star systems have just as many planets as single star systems? That was a rather non-intuitive thing that I know the astrophysicists weren't expecting.)

-the other Doug

This is a semantic point. In the U.S. space program there is a tradition to call any spacecraft's operational phases (from launch through end of mission) the "flight," regardless of whether they take place in open space or on the surface of (or even in close proximity to) another body.

Thus, even post-landing, this tradition would have all of our current Curiosity operations be called "the Flight of the Mars Science Laboratory." From now until end of mission, we are in the surface operations phase of the flight, but per this tradition, we are still in the midst of an operational flight.

-the other Doug

Curiosity isn't looking for living things, really, you're right. But any Mars lander with a camera can find an obvious fossil within the camera's field of view.

We obviously won't get into any kind of discussion as to whether or not anything in the tens of thousands of pictures returned from the Martian surface resembles a fossil -- that's so far outside of our rules here it's not even funny. Just wanted to point out that a camera will generally see what is there, and not see what's not there.

-the other Doug

Ummm... can the APXS detect deuterium at all, much less analyze its relative abundance? An Astronomy Online review of the MER APXSes (which, as I understand it, are quite similar to the one on Curiosity) says the following:



I don't see H mentioned anywhere in the list of elements to which the APXS is sensitive. Obviously, it's not a definitive list, but... just sayin', I thought APXS only gave relative atomic abundances and only for a selected set of elements to which the detectors are sensitive. I didn't think it actually gave molecular abundance information.

-the other Doug

Also, depending on the density of the foam used in the shell, it could possibly have been blown a little in the wind over the years. Especially if it was oriented at any point with the hollow end pointed towards the direction of the prevailing winds.

-the other Doug

Well... the early Soviet Luna moon landers (Lunas 9 and 13 in particular), which were configured somewhat similarly to the Mars 3 lander, did have airbags. Are we certain that Mars 3 did not employ them?

-the other Doug

This, of course, would not be the first time a Mars probe has had some kind of "trim flaps" at the tips of its solar panels, and the reasoning was similar, if not exactly the same.

Mariners 3 and 4 (of which only Mariner 4 survived launch) had small triangular trim tabs at the ends of its solar panels. This was not for aerodynamics, but for pressure dynamics. They were used to take advantage of the pressure of the solar wind to help keep the spacecraft stable.

IIRC, the stabilizing force was so minuscule that follow-on probes omitted this kind of feature. They weren't worth the weight penalty. Now that we're dealing with much thicker gasses than the solar wind (with aerobraking maneuvers), adding stabilizing tabs apparently becomes worth the weight penalty.

-the other Doug

Curiosity -- the OCD rover!



-the other Doug

What we need during this interlude is music. May I suggest...

Eine Kleine Bohrermusik?



-the other Doug

A pretty good (at least from a distance) drive-able MER model is also featured in a commercial for, I believe, General Electric. It's wandering through an airport and then rolls right up to the maw of a big jet engine. I expected the engine to start and the little MER to fly up into it from the wind into the air intake...

-the other Doug

Are you still able to see the comet naked-eye, Stu? Or does it require a pretty long exposure to become visible in your images?

I, alas, ran across cloudy western skies in the evenings for the entire time PANSTARRS would have been naked-eye visible through city lights here in Minneapolis. So, your pictures (and those of others) are all I have seen of it.

-the other Doug

A guy named Greg Stekelman appears to have created a faux-BBC News web page that he then distributed as an April Fool's joke. It was so funny I wanted to share it here (and besides, the graphic must have been taken from a spacecraft, right?)...





-the other Doug

The problem is that simply reversing the orbit dynamics in time gets to the point where you require another body in the equation to effect the orbital capture. And it's impossible to tell what those dynamics were.

Myself, I prefer the theory that a fairly large and rapidly spinning body broke up when it passed within Mars' Roche limit. Part of of it impacted Mars, part of it achieved escape velocity, and two pretty big chunks ended up in stable orbits. Other chunks ended up in unstable orbits and eventually hit Mars.

At what time this happened is probably most easily constrained by looking at the age of craters/basins that could have been caused by such a catastrophic impact. You can place the event at almost any point in the time-reversed orbital history of the moons by simply adjusting the size, speed and trajectory of the body that came apart, so such a reverse-time orbital analysis would be less useful for constraining the timeframe, I would imagine.

-the other Doug

Phoenix also identified carbonates as one of the constituents of the soil at its landing site. Only something like two or three percent, IIRC, but definitely there and detectable.

Of course, when you have a CO2 atmosphere, I imagine there are a heck of a lot of ways to make carbonates.

-the other Doug

"We'll finish up here at John Klein then hit the road for Mt. Sharp."

Grotzinger was very careful, though, to stress that their planning is discovery-driven, and that a second drill sample (which will not happen until after conjunction, in May) may lead to another sample location or two in the Yellowknife Bay area before heading on the road.

Also, some initial planning has been done to stop and more carefully analyze a few interesting things that they passed by on the way from Bradbury Landing to Yellowknife. Sort of a lingering send-off to the road trip.

-the other Doug

Great to hear from you, Rob. A hearty cheer for all of you involved in this enterprise.

My initial takeaways, here -- MSL is fully commissioned and everything works; the rock sample appears to have been about 20% smectite, a phyllosilicate clay which only forms in neutral-pH water; still seeing chloromethanes and dichloromethanes, just like at Rocknest, so it gets a little less likely that we're seeing contamination; one of the possible run-off gas processes could be the result of dissolution of carbonate materials.

Also, from early in the presser, Grotzinger saying that Mt. Sharp "used to be" the primary science goal of the mission. ???!!!

-the other Doug

edit -- actually, I think the way Grotzinger put it was that the alluvial fan area was defined as a secondary science objective, sort of as a way to sell the site seeing as how reaching Mt. Sharp would take a fair amount of time. He then said something like the alluvial fan site "used to be the secondary goal, and Mt. Sharp had been our primary science destination." I do not think he said that Mt. Sharp has been demoted, just that the current location is now seen as much more important than before. And, hey, the guy just said "We will still go to Mt. Sharp, and we think we'll get there." dvd

Smectite!

-the other Doug

Just to try and wrap up this digression in the topic a bit, I will point out that there are tons of science popularizers out there plying the trade, from the late, great Carl Sagan to Brian Cox to Neil deGrasse Tyson to, gods help us, Michio Kaku. And a whole phalanx of scientists and science / science fiction writers who appear regularly as "support troops" in science-oriented programming. They do a pretty good job of making the "boring" stuff interesting and approachable to a large segment of the population.

Just sayin' that the "trades" (like AW&ST or, these days, Space.com) are written for the small, knowledgeable niche audience that wants and needs the jargon, the "boring" scientific details, the engineering activities, etc. (You know, people like us.) The main science popularizers operate on less of a breaking-news basis and more of a documentary basis. And eventually, the really cool things we'll find out about at tomorrow's presser will find their way into the documentary world and raise, just a little bit, the overall level of knowledge and interest in the subject amongst the great, unwashed masses.

To be honest, I'm not sure we've had a really good science popularizer doing breaking-news kind of coverage since James Burke. The best of those that have come since do educational and documentary film, and only rarely are used to discuss breaking news stories.

-the other Doug

I find it interesting that in the histories of the development of the Saturn V rocket, a big deal is always made of the fact that if the rocket were to ever explode on the launch pad, it would result in a blast the size of a "fair-sized nuclear weapon." However, the yield estimate for an exploding Saturn V was given as between 3 and 5 kilotons.

So, to put it into perspective, this meteor exploded in a blast roughly 100 times more powerful than an exploding Saturn V rocket...

-the other Doug

If the answer to this is really obvious, please excuse me. But the MER-B landing site was selected because of a strong indicator from orbital sensors of hematite in the Meridiani area.

If the ubiquitous dust on Mars is hematitic, then how would the Meridiani area stand out? Is gray hematite (as in the Meridiani concretions) far easier to spot from orbit than red hematite? I always thought the two were rather similar, chemically.

Just wonderin'...

-the other Doug