1
00:00:10,790 --> 00:00:07,510
did earth have two moons

2
00:00:12,789 --> 00:00:10,800
presented by science at nasa

3
00:00:14,709 --> 00:00:12,799
nothing stirs the soul of poets and

4
00:00:17,430 --> 00:00:14,719
lovers like the sight of a full moon

5
00:00:19,830 --> 00:00:17,440
rising on a warm autumn night

6
00:00:21,429 --> 00:00:19,840
nothing that is except the sight of two

7
00:00:23,189 --> 00:00:21,439
moons rising

8
00:00:25,670 --> 00:00:23,199
if a paper published recently in the

9
00:00:27,750 --> 00:00:25,680
journal nature is right two moons once

10
00:00:30,390 --> 00:00:27,760
graced the night skies of earth

11
00:00:31,830 --> 00:00:30,400
the idea has not been proven but it is

12
00:00:33,190 --> 00:00:31,840
drawing the serious attention of

13
00:00:35,430 --> 00:00:33,200
researchers

14
00:00:37,030 --> 00:00:35,440
it's an intriguing idea says david smith

15
00:00:38,310 --> 00:00:37,040
of the massachusetts institute of

16
00:00:39,990 --> 00:00:38,320
technology

17
00:00:41,750 --> 00:00:40,000
and it would be a way to explain one of

18
00:00:42,709 --> 00:00:41,760
the great mysteries of the earth moon

19
00:00:45,590 --> 00:00:42,719
system

20
00:00:48,310 --> 00:00:45,600
the moon is strangely asymmetrical

21
00:00:50,869 --> 00:00:48,320
the moon's near side facing us

22
00:00:52,790 --> 00:00:50,879
is dominated by vast smooth seas of

23
00:00:54,950 --> 00:00:52,800
ancient hardened lava

24
00:00:57,029 --> 00:00:54,960
the moon's far side on the other hand is

25
00:00:58,709 --> 00:00:57,039
marked by mountainous highlands

26
00:01:00,790 --> 00:00:58,719
researchers have long struggled to

27
00:01:02,310 --> 00:01:00,800
explain why the two sides of the moon

28
00:01:04,630 --> 00:01:02,320
are so different

29
00:01:07,350 --> 00:01:04,640
and the two moon theory introduced by

30
00:01:09,510 --> 00:01:07,360
planetary scientists martin jotzi and

31
00:01:11,910 --> 00:01:09,520
eric asforg of the university of

32
00:01:13,109 --> 00:01:11,920
california at santa cruz is the latest

33
00:01:15,190 --> 00:01:13,119
attempt

34
00:01:17,670 --> 00:01:15,200
nasa's grail mission launched from the

35
00:01:19,830 --> 00:01:17,680
kennedy space center on september 10th

36
00:01:21,350 --> 00:01:19,840
could help unravel the mystery

37
00:01:23,590 --> 00:01:21,360
smith is the deputy principal

38
00:01:27,190 --> 00:01:23,600
investigator for grail which stands for

39
00:01:29,670 --> 00:01:27,200
gravity recovery and interior laboratory

40
00:01:32,310 --> 00:01:29,680
grail consists of two spacecraft that

41
00:01:34,390 --> 00:01:32,320
will orbit the moon in tandem precisely

42
00:01:36,069 --> 00:01:34,400
mapping the moon's gravitational field

43
00:01:38,149 --> 00:01:36,079
and thus revealing how the moon's

44
00:01:40,310 --> 00:01:38,159
interior is layered

45
00:01:42,310 --> 00:01:40,320
among other things this could test the

46
00:01:44,310 --> 00:01:42,320
two moon theory

47
00:01:46,469 --> 00:01:44,320
most scientists believe that when a

48
00:01:48,310 --> 00:01:46,479
mars-sized object crashed into our

49
00:01:50,789 --> 00:01:48,320
planet about four and a half billion

50
00:01:53,030 --> 00:01:50,799
years ago the resulting debris cloud

51
00:01:55,270 --> 00:01:53,040
coalesced to form the moon

52
00:01:58,069 --> 00:01:55,280
jetsey and asphalt say that the debris

53
00:02:00,310 --> 00:01:58,079
cloud actually formed two moons

54
00:02:02,230 --> 00:02:00,320
a second smaller chunk of debris landed

55
00:02:04,550 --> 00:02:02,240
in just the right orbit to pace the

56
00:02:06,709 --> 00:02:04,560
bigger moon around earth

57
00:02:08,869 --> 00:02:06,719
normally such moons accrete into a

58
00:02:10,710 --> 00:02:08,879
single body shortly after formation

59
00:02:12,630 --> 00:02:10,720
explains smith but the new theory

60
00:02:14,309 --> 00:02:12,640
proposes that the second moon ended up

61
00:02:15,990 --> 00:02:14,319
at one of the lagrange points in the

62
00:02:17,510 --> 00:02:16,000
earth moon system

63
00:02:19,589 --> 00:02:17,520
lagrange points are a bit like

64
00:02:22,229 --> 00:02:19,599
gravitational fly traps

65
00:02:24,630 --> 00:02:22,239
they can hold an object for a long time

66
00:02:26,550 --> 00:02:24,640
but not necessarily forever

67
00:02:28,390 --> 00:02:26,560
the second moon eventually worked its

68
00:02:29,510 --> 00:02:28,400
way out and collided with its bigger

69
00:02:31,110 --> 00:02:29,520
sister

70
00:02:33,190 --> 00:02:31,120
the collision occurred at such low

71
00:02:34,229 --> 00:02:33,200
velocity that the impact did not form a

72
00:02:37,270 --> 00:02:34,239
crater

73
00:02:39,030 --> 00:02:37,280
instead the smaller moon went splat

74
00:02:40,229 --> 00:02:39,040
forming the contemporary far side

75
00:02:44,309 --> 00:02:40,239
highlands

76
00:02:46,630 --> 00:02:44,319
lost moon's remains

77
00:02:48,550 --> 00:02:46,640
when grail examines the lunar far side

78
00:02:50,309 --> 00:02:48,560
will it find evidence of a long-lost

79
00:02:51,670 --> 00:02:50,319
moon splattered across the ancient grey

80
00:02:53,350 --> 00:02:51,680
landscape

81
00:02:55,190 --> 00:02:53,360
for answers to this and other

82
00:02:57,110 --> 00:02:55,200
soul-stirring questions as the grail