火星山洞

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解释 :在火星上发现的黑洞都太黑了，以致里面有什么都看不到。很有可能，这些黑点都是进入深层地底洞穴的入口，还有能力保护火星生命，如果它存在的话。上面这张照片中那个不平常洞穴是在火星上巨大的阿爾西亞山火的侧翼上发现的。这张摄于三周前的图片是目前还在火星轨道上运行的火星轨道探测器上的HiRISE(高解析影像及科学实验相机-- High Resolution Imaging Science Experiment)设备拍出来。洞穴最初是在火星奥德赛太空船的低解析度照片上确认到的。上面这个洞穴的大小大约是一个足球大小，而且它太深了，以致太阳光都照不到。像这些洞和地下洞穴可能是以后的探测器、机器人甚至是下一代的人类行星际的探测活动。
Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2007 May 28

A Hole in Mars
Credit: NASA, JPL, U. Arizona

Explanation: Black spots have been discovered on Mars that are so dark that nothing inside can be seen. Quite possibly, the spots are entrances to deep underground caves capable of protecting Martian life, were it to exist. The unusual hole pictured above was found on the slopes of the giant Martian volcano Arsia Mons. The above image was captured three weeks ago by the HiRISE instrument onboard the Mars Reconnaissance Orbiter currently circling Mars. The holes were originally identified on lower resolution images from the Mars Odyssey spacecraft, The above hole is about the size of a football field and is so deep that it is completely unilluminated by the Sun. Such holes and underground caves might be prime targets for future spacecraft, robots, and even the next generation of human interplanetary explorers.

Tomorrow's picture: sprawling spiral

[ 本帖最后由 夜空 于 2007-5-29 11:08 编辑 ]

夜空

顾着看电视剧和动画片，到现在才翻译完，有点迟了。质量不大好，凑合着看吧:lol

夜猫子

“上面这个洞穴的大小大约是一个足球大小”？？？ 有点不相信啊……

夜空

原帖由 夜猫子 于 2007-5-29 08:24 发表
“上面这个洞穴的大小大约是一个足球大小”？？？ 有点不相信啊……

这里有较详细的图片资料，点击图片查看大图
http://www.planetary.org/blog/article/00000984/




[ 本帖最后由 夜空 于 2007-5-29 10:58 编辑 ]

夜空

我把文字转过来了，迟些附上翻译
Today's set of image releases from the Mars Reconnaissance Orbiter HiRISE team included this one, of a fairly bland-looking lava plain to the northeast of Arsia Mons. Bland, that is, except for a black spot in the center. What's that black spot? It's a window onto an underground world.

Click to enlarge > Cave entrance on the flank of Arsia Mons In this HiRISE image captured on May 7, 2007, a black spot mars the flank of Arsia Mons. The spot is most likely a skylight onto a subterranean cavern. Credit: NASA / JPL / U. Arizona

This black spot is one of seven possible entrances to subterranean caves identified on Mars by Glen Cushing, Tim Titus, J. Judson Wynne and Phil Christensen in a paper they presented at the Lunar and Planetary Science Conference in March (PDF format, 322k). Here's the figure from their paper that shows the seven caves, which they refer to by the names Dena, Chloe, Wendy, Annie, Abbey, Nikki, and Jeanne:

Click to enlarge > Possible cave entrances on Mars Seven dark spots seen in Mars Odyssey THEMIS images could be the entrances to underground caves on Mars. The researchers who identified these caves have given them the following names: Dena (-6.084 N, 239.061 E) Chloe (-4.926 N, 239.193 E) Wendy (-8.099 N, 240.242 E) Annie (-6.267 N, 240.005 E) Abbey & Nikki (-8.498 N, 240.349 E) Jeanne (-5.636 N, 241.259 E) Credit: NASA / JPL / U. Arizona / G. Cushing et al. 2007

Their identifications were based upon Mars Odyssey THEMIS images, which achieve resolutions of a little better than 20 meters per pixel; having spotted the caves, they requested that the sharper-eyed HiRISE camera on Mars Reconnaissance Orbiter target the spots for more detailed imaging. The image above is the first one of these, and it shows the cave entrance called Jeanne. So what more can we learn from the HiRISE image? Let's check it out at full resolution (you'll have to click to enlarge for the full glory of 25 centimeters per pixel, a number I still goggle at every time I think about it).

Click to enlarge > Cave entrance on the flank of Arsia Mons At its highest resolution of 25 centimeters per pixel, the HiRISE camera can see the detailed shape of the slightly scalloped edge of a hole on the flank of Mars' Arsia Mons (left), but no amount of image enhancement (right) can bring out any further details inside the hole. That means that the walls of the cave are overhanging -- the cave is larger below the ground than the entrance we can see at the surface -- and that it is very deep. Mars' dusty atmosphere produces enough scattered light that "skylight" would illuminate the floor of a shallow cavern well enough for HiRISE to detect it. Credit: NASA / JPL / U. Arizona

The hope for the HiRISE images was that we could see some details from inside the hole. But as you can see by the highly stretched version at right, there is absolutely nothing visible inside that hole. It's black black black black black. HiRISE is a very sensitive instrument, and Mars' dusty atmosphere scatters quite a bit of light around, so there is certainly light entering that cave hole and bouncing around the interior. But it seems that the cave is so big and so deep that almost none of the light that enters the cave comes out. It's deep, and it's big; the hole that we see really is just a skylight on a big subterranean room. How big? We'll never know for sure without visiting it, but I expect that Cushing and his coauthors and the HiRISE team will be crunching the numbers on the illumination conditions and the sensitivity of the camera to put a lower limit on how deep that cave must be for HiRISE to be able to see nothing at all inside it.

Think about that. All these orbiters at Mars, and most of them are just seeing the surface and atmosphere. To be sure, there are two instruments up there -- MARSIS on Mars Express and SHARAD on Mars Reconnaissance Orbiter -- that are probing the shape of the subsurface with ground-penetrating radar. But neither of those instruments have the resolution necessary to tell us what the inside of this cave looks like. It might as well be in the greatest depths of space. Here there be dragons. What's down there? Are there stalactites and stalagmites and crystals, or is it just a vast open room or tunnel?

Maybe these spots will be explored by Martian speleologists someday. But that day is a distant one, I'm sure. Earth speleologists are only now exploring some of the biggest holes in our world.

夜猫子

哈哈,100M,应该是个足球场大小吧, 总不会有这么大的足球吧?:lol

夜空

原帖由 夜猫子 于 2007-5-29 16:33 发表
哈哈,100M,应该是个足球场大小吧, 总不会有这么大的足球吧?:lol

嗯，一时看漏眼，翻译错了:lol

疑神疑鬼

没关系　谢谢你的翻译

b777200

派个机器人进去，看看有没有火星人！:lol :lol