ESA and JAXA release Mercury eyecandy, courtesy of spacecraft BepiColumbo

The European Space Agency (ESA) and Japan Aerospace Exploration Agency's (JAXA) joint mission BepiColombo sent back its first photos of Mercury on Friday as it completed the fourth of nine planetary flybys enroute to study the solar system's smallest and innermost planet. The spacecraft passed a mere 199km from Mercury's …

[hoola]

Amazing achievement

This has been years in the planning and where I work has instruments on the platform.

Mercury is a really difficult target because you are inbound to the sun and gravity becomes your worst enemy due to the acceleration. That it is travelling at 60KMs at is fasted so that it can catch up with Mercury is amazing. Then it has to slow down enough to enter orbit. even allowing for some reduction in speed, 60KMs with a separate of 200KM is not much room for error.

Hopefully over the next few years all will continue to operate normally so they can get into the designed orbit round Mercury.

[UCAP]

Re: Amazing achievement

Not certain that gravity is THE worst enemy - the incident solar radiation (light, heat and assorted other nasties) are also very high on that list. Mercury missions all have on problem in common - how to protect the delicate bits (instruments, control systems, ...) from the Sun.

[Eclectic Man]

Re: Amazing achievement

I'm guessing that imaging the sunlit side of Mercury requires some serious optical filtering to deal with the albedo compared with imaging the unlit side. The good old 'sunny 16 rule'* won't work on Mercury.

Excellent news and fingers crossed for the future of the mission.

*The 'sunny 16 rule' was used by analogue photographers to judge the correct exposure for sunlit subjects before reliable light meters were introduced. Basically the 'speed' of a film emulsion measured in ASA was the reciprocal of the correct shutter speed at f/16. So a 100ASA film would be correctly exposed for a subject in sunlight at 1/100 s at f/16.

[bombastic bob]

Re: Amazing achievement

I'm guessing that imaging the sunlit side of Mercury requires some serious optical filtering to deal with the albedo compared with imaging the unlit side

2 words: pinhole camera. That should improve focus AND limit the amount of light on the sensor, to avoid some of the bad effects of super-bright light. As for the dark side, I guess you need variable arpeture or similar.

But you would also get shadowing on the sunny side. So you'd need both light and dark side images, and with its slow rotation (sidereal day is ~58 earth days long withy an ~88 earth day orbit) that';s not quite synchronized with its orbit, it would take a really long time (~170 earth days) to get both light-side and dark-side images. [apparently Venus' day is even longer and effectively the sun goes BACKWARDS with respect to the direction the stars go, as seen from the surface of the planet].

[Anonymous Coward]

Re: Amazing achievement

Indeed amazing. But not very enlightening. Yet.

BepiColumbo's first flyby didn't tell us much new that, coincidently, Bepi Columbo hadn't already described from ground based observations,

But if the mission is successful in deploying the orbiters, we will gain a wealth of knowledge.

[Gene Cash]

Name

Today I learned that it's named after the bloke that invented gravity assists, as well as doing a lot of astronomy on Mercury.

[Graham Dawson]

Re: Name

That's amazing. How did he get his telescope all the way out there?

[E 2]

You'd think a bunch of people as smart as these could shoot pictures without the damned satellite disk in the way, innit?

[Eclectic Man]

In an interview on BBC Radio 4 a senior mission scientist stated that they were only using low resolution cameras until they achieved orbit, when the best cameras would be deployed and able to image the planet.

[bombastic bob]

Another reason why Mercury may be interesting to Earthlings

I have long suspected that Mercury may contain higher concentrations of heavier materials in its crust. Note I said MAY because there are a lot of geological factors that might be put into play here.

First, Mercury being closer to the sun is likely to have its lighter materials blown away during planet formation. As such, inner planets are rocky, outer planets are gaseous. Not always, but that's an observable pattern, right?

Second, Mercury may have remained volcanic for a longer period of time. This is both good and bad. Kimberlite pipes contain diamonds but were once (as I understand it) magma tubes from the mantle to the surface. Other 'heavy' things can also end up in (or near) magma/volcanic pipes as I understand it, including gold [though the mechanism for it getting there is a bit different]. If Mercury remained volcanic for longer, there may be a LOT more of these with accessible minerals in them (more than on earth). And if that is the case, the volcanic structures could be indicators of where to start digging...

Alternately, with a molten surface that lasts longer than on Earth, all of the heavy elements could have sunk to the center of the core, giving you LESS of it at the surface where we might actually reach it.

Still, I would bet that at the poles you'd have many areas that never see sun, others that only see a fraction of sunlight, and everywhere else, 100+ effective mining days available for robots to locate and extract things and launch them back to Earth. It may become the geological find of the millenium.

[aks]

Re: Another reason why Mercury may be interesting to Earthlings

"extract things and launch them back to Earth"

Why? All of that good stuff needs to be used to build ginormous spacecraft. :)

[Anonymous Coward]

Re: Another reason why Mercury may be interesting to Earthlings

Don't even hint Mercury might contain diamonds, the Diamond Cartel will blow it up!

[HelpfulJohn]

Re: Another reason why Mercury may be interesting to Earthlings

Well, to give them another idea: Jupiter *might* contain as its core a diamond larger than the Earth.

There, De Beers, now you can have a new hobby ...

[Eclectic Man]

Re: Another reason why Mercury may be interesting to Earthlings - Gold and Diamonds

The retail prices of both gold and diamonds are artificially high due to the jewellery business. Cheap diamonds can be made commercially (although they are easily distinguished from natural diamonds in the correct lighting). There is actually gold in sea water, but the cost of retrieval is too high. The enormous costs of getting anything back to Earth from Mercury would probably make it uneconomic to mine Mercury for anything on a commercial scale.

However, the science would be wonderful if we could put a rover on Mercury like we have several times on the Moon and Mars.

[Citizen99]

Re: Another reason why Mercury may be interesting to Earthlings

Robots ? I was hoping for the Dwarves with their picks and shovels.

[Potemkine!]

atmosphere-less planet faces the sun reaching 430°C while the dark side keeps extremely cold temperatures of -185°C.

So it means that in the transition zone there should be an area with moderate temperature where humans could live. If there's waters into craters near the poles, it could be even sustainable.

I've got a list of people to send there once the colonization starts.

As the only planet aside from Earth with a global magnetic field

Haven't Jupiter and Saturn a global magnetic field too? :~

This sentence made me realize that Venus has none. In one hand, I read that Mars lost its atmosphere because it lost its global magnetic field. In the other, Venus has probably the thickest atmosphere of the Solar system. Is this just because Venus' gravity is higher?

[UCAP]

Haven't Jupiter and Saturn a global magnetic field too?

You are right; Jupiter and Saturn (as well as Uranus and Neptune) have substantial magnetic fields, particularly Jupiter (if you could see it from Earth, Jupiter's magnetic field would be larger than the Moon). I suspect the article meant inner-system planets, not gas giants.

Regarding Venus & Mars, Mars' magnetic field died when Mars' core froze - the planet is too small to keep the core molten for very long (in astronomical terms). In the case of Venus, it is suspected (but not confirmed) that the magnetic "dynamo" stopped working because Venus rotates too slowly (a day on Venus is actually longer than its year). Venus is basically the same size as the Earth with approximately the same gravity, so that has no effect on the planet's magnetic field.

[Potemkine!]

Thanks for the explanations.

Venus is basically the same size as the Earth with approximately the same gravity, so that has no effect on the planet's magnetic field.

I wasn't clear enough. I meant is Venus's gravity strong enough to keep its atmosphere even if it hasn't a magnetic shield to protect it from solar particles? If solar particles are strong enough to blow Mars atmosphere, why isn't the result the same for Venus. Adding to that that venus being closer and bigger, I guess it gets hit by more solar particles than Mars.

[UCAP]

Thanks for the clarification.

The answer is, mostly yes. Venus is more than capable of holding on to its atmosphere for the expected life of the Solar System, however the solar wind is slowing stripping the top layers off one molecule at a time. However Venus has a lot of atmosphere to play with, so the slow loss is not hurting it in the long run.

[ThatOne]

> in the transition zone there should be an area with moderate temperature

There is no atmosphere, so the transition zone is the place where you get scorched and deep frozen at the same time: If you were standing there, your parts illuminated by the sun would be at 430°C, the parts in the shadow at -185°C. Not the general definition of "moderate temperature"...

I'm not sure about radiation either: Chances are at this distance the solar wind is dense enough to sterilize (kill) everything in mere hours. But that's a mere supposition, I don't know. What I'm sure though is that Mercury isn't a place for humans. We could build bases (deep underground) there, but we'd need a really, really compelling reason ("Unobtainium" level compelling, common minerals won't cut it, especially since you'd need to pull them out of the sun's gravity well).

[HelpfulJohn]

"... but we'd need a really, really compelling reason "

Because it's there?

Were humans ever to colonise the bits of the Solar System that are relatively easy to use, and were they also to build city-farms in Earth orbits and bobbing about in the

Asteroid Belts and Trojan Zones, Mercury would get used simply because it's big, often heated a little, has loads of things to build with, places to explore and sights to

see and it has a small source of photo-electric power that could be useful.

That she's a damned hard-to-get-to place only makes her more enticing. Humans adore having to work to get to places. The challenge makes the result seem all the

sweeter. Or so I'm told.

Personally, I'd rather Green Venus.