1
00:00:09,830 --> 00:00:07,349
the sleepy hollows of mercury presented

2
00:00:12,070 --> 00:00:09,840
by science at nasa

3
00:00:14,549 --> 00:00:12,080
the word sleepy hollow have been steeped

4
00:00:16,230 --> 00:00:14,559
in mystery ever since the 19th century

5
00:00:18,310 --> 00:00:16,240
when washington irving wrote about the

6
00:00:20,870 --> 00:00:18,320
meeting of ichabod crane and the

7
00:00:21,910 --> 00:00:20,880
headless horseman in a secluded european

8
00:00:23,830 --> 00:00:21,920
clan

9
00:00:25,589 --> 00:00:23,840
of course that was fiction

10
00:00:26,550 --> 00:00:25,599
on the planet mercury the hollows are

11
00:00:28,550 --> 00:00:26,560
real

12
00:00:30,950 --> 00:00:28,560
orbiting mercury nasa's messenger

13
00:00:33,590 --> 00:00:30,960
spacecraft has just discovered strange

14
00:00:36,389 --> 00:00:33,600
hollows as steeped in mystery as the one

15
00:00:38,549 --> 00:00:36,399
irving wrote about so many years ago

16
00:00:41,110 --> 00:00:38,559
high-resolution images reveal thousands

17
00:00:43,030 --> 00:00:41,120
of peculiar depressions at a variety of

18
00:00:45,510 --> 00:00:43,040
longitudes and latitudes

19
00:00:49,029 --> 00:00:45,520
ranging in size from 60 feet to more

20
00:00:49,990 --> 00:00:49,039
than a mile across and 60 to 120 feet

21
00:00:52,310 --> 00:00:50,000
deep

22
00:00:54,069 --> 00:00:52,320
no one knows how they got there

23
00:00:56,389 --> 00:00:54,079
the hollows of mercury were a major

24
00:00:58,549 --> 00:00:56,399
surprise says david blewett science team

25
00:01:00,709 --> 00:00:58,559
member from the johns hopkins university

26
00:01:02,229 --> 00:01:00,719
applied physics laboratory

27
00:01:04,630 --> 00:01:02,239
we've been thinking of mercury as a

28
00:01:06,710 --> 00:01:04,640
relic a place that's not changing much

29
00:01:08,310 --> 00:01:06,720
anymore but the hollows appear to be

30
00:01:10,630 --> 00:01:08,320
much younger than the craters in which

31
00:01:12,310 --> 00:01:10,640
they are found and that means mercury's

32
00:01:13,910 --> 00:01:12,320
surface is still evolving in a

33
00:01:15,670 --> 00:01:13,920
surprising way

34
00:01:17,109 --> 00:01:15,680
mars reconnaissance orbiter spotted

35
00:01:19,910 --> 00:01:17,119
similar depressions in the carbon

36
00:01:22,550 --> 00:01:19,920
dioxide ice at mars south pole giving

37
00:01:25,510 --> 00:01:22,560
that surface a swiss cheese appearance

38
00:01:28,469 --> 00:01:25,520
but on mercury they're found in rock and

39
00:01:30,069 --> 00:01:28,479
often have bright interiors and halos

40
00:01:32,550 --> 00:01:30,079
we've never seen anything quite like

41
00:01:34,069 --> 00:01:32,560
this on a rocky surface he says

42
00:01:36,469 --> 00:01:34,079
if you could stand in one of these

43
00:01:38,950 --> 00:01:36,479
sleepy hollows on mercury's surface

44
00:01:42,550 --> 00:01:38,960
you'd find yourself like ichabod crane

45
00:01:44,789 --> 00:01:42,560
in a quiet still haunting place with a

46
00:01:46,550 --> 00:01:44,799
jet black sky above your head

47
00:01:48,630 --> 00:01:46,560
there's essentially no atmosphere on

48
00:01:50,389 --> 00:01:48,640
mercury says blewitt so the hollows

49
00:01:51,350 --> 00:01:50,399
could not have been carved by wind or

50
00:01:53,510 --> 00:01:51,360
rain

51
00:01:55,910 --> 00:01:53,520
other forces must be at work

52
00:01:58,310 --> 00:01:55,920
as the planet closest to the sun mercury

53
00:01:59,590 --> 00:01:58,320
is exposed to fierce heat and extreme

54
00:02:01,590 --> 00:01:59,600
space weather

55
00:02:02,789 --> 00:02:01,600
blewitt believes these factors may play

56
00:02:04,870 --> 00:02:02,799
a role

57
00:02:06,550 --> 00:02:04,880
a key clue he says is that many of the

58
00:02:09,270 --> 00:02:06,560
hollows are associated with central

59
00:02:10,710 --> 00:02:09,280
mounds or mountains inside mercury's

60
00:02:12,790 --> 00:02:10,720
impact craters

61
00:02:14,790 --> 00:02:12,800
these so-called peak rings are thought

62
00:02:17,110 --> 00:02:14,800
to be made of material forced up from

63
00:02:18,070 --> 00:02:17,120
the depths by the impact that formed the

64
00:02:20,150 --> 00:02:18,080
crater

65
00:02:22,309 --> 00:02:20,160
excavated material could be unstable

66
00:02:24,150 --> 00:02:22,319
when it finds itself suddenly exposed at

67
00:02:25,990 --> 00:02:24,160
mercury's surface

68
00:02:28,470 --> 00:02:26,000
certain minerals for example those that

69
00:02:30,710 --> 00:02:28,480
contain sulfur and other volatiles would

70
00:02:33,670 --> 00:02:30,720
be easily vaporized by the onslaught of

71
00:02:36,470 --> 00:02:33,680
heat solar wind and micrometeoroids that

72
00:02:38,710 --> 00:02:36,480
mercury experiences on a daily basis

73
00:02:41,430 --> 00:02:38,720
messenger has found mercury unexpectedly

74
00:02:43,589 --> 00:02:41,440
rich in sulfur explains blewitt

75
00:02:45,910 --> 00:02:43,599
perhaps the sulfur is vaporizing leaving

76
00:02:47,509 --> 00:02:45,920
just the other minerals and therefore

77
00:02:48,710 --> 00:02:47,519
weakening the rock and making it

78
00:02:50,550 --> 00:02:48,720
spongier

79
00:02:53,509 --> 00:02:50,560
then the rock would crumble and erode

80
00:02:55,350 --> 00:02:53,519
more readily forming these depressions

81
00:02:57,190 --> 00:02:55,360
more data from messenger and further

82
00:02:58,869 --> 00:02:57,200
study by the mission science team could

83
00:03:01,270 --> 00:02:58,879
reveal the answer

84
00:03:03,589 --> 00:03:01,280
meanwhile blewett wonders what other

85
00:03:05,350 --> 00:03:03,599
surprises does mercury hold

86
00:03:07,750 --> 00:03:05,360
the sleepy hollows of the innermost

87
00:03:10,229 --> 00:03:07,760
planet may be just the beginning