Sky & Telescope - June 2024 - 52
JUNE 2024 OBSERVING
Exploring the Solar System by Charles A. Wood
Carpenter
60°
Ch'5
Ap15
Ap17
L24
Copernicus
Cavalerius
Apex
Ap12
Bullialdus
Stevinus
Hainzel A
Tycho
-60°
-30°
Eratosthenes
Ap11
Ap14
Ap16
L16
Antapex
0°
0.7
0.8
0.9
1
30°
1.1
1.2
Craters Younger Than We Thought
A
New crater counts help to revise our understanding of lunar chronology.
mong the most critical data
required to understand lunar history
are the approximate times that
major lunar features formed. The most
accurate ages come from radiometric
analyses of lunar samples. Unfortunately,
samples from only 11 sites have
been returned to Earth by the lunar
programs of the U.S., the Soviet Union,
and China.
For the rest of the Moon, the standard
method used to estimate crater ages and
other formations is to count the number
of impact craters in an area of interest.
This technique assumes that craters
form all the time, and therefore older
surfaces have more craters and younger
regions have fewer. Impact craters have
formed throughout the last 4.5 billion
years, though not at a constant rate.
To determine how the crater production
rate (CPR) changed over time, scientists
count the number of impact craters
with diameters larger than 1 kilometer
that are present per square km. This
is called the N(1) value. For the areas
where lunar samples were returned to
Earth, their absolute ages were measured
52 JUNE 2024 * SKY & TELESCOPE
in laboratories. A graph of N(1) and age
data shows how the CPR decreased over
lunar history, with a very high cratering
rate about 4 billion years ago and a much
lower, near-constant rate for roughly the
last 3 billion years.
Astronomers establish an estimated
age (called the model age) for any feature
lacking radiometrically dated samples
by counting craters to derive their N(1)
values, then plotting them on a graph.
Having done so, scientists determined
hundreds of model ages for features. For
instance, the east side of Sinus Iridum
is about 3.35 billion years old, while the
Revised Crater Ages
(billions of years)
Crater
Carpenter
Cavalerius
Hainzel A
Bullialdus
Eratosthenes
Stevinus
Neukum
age
3.1
3.1
3
3.7
3.3
0.9
Lagain
age
2.4
2.5
2.5
3.6
3.3
1.0
pThis map illustrates the asymmetry of
lunar cratering rates, with red colors showing
higher-than-average rates and blues for lowerthan-average
ones. The two white circles mark
the apex or leading edge (left) and antapex or
trailing face (right) of lunar motion. Black and
yellow circles indicate 11 age-dated samples
used for chronology calibration; green circles
are craters listed in the table below.
west side is 350 million years younger.
Both values match that of adjacent
Mare Imbrium lavas, which flowed
downhill into Iridum.
As marvelous as the ability to ascertain
a model age is, there are uncertainties
that sometimes lead to disparate
estimates. For example, researchers often
count different numbers of craters in the
same area. This can be due to the difficulties
in deciding if a feature is a crater,
a degraded crater, or random topography.
They also sometimes disagree if a crater
is a primary impact or a secondary crater
that formed from the fallback of materials
ejected from a primary impact and
thus should be ignored. Another variable
arises when researchers develop different
mathematical fits to N(1) values and
absolute-age data. In extreme cases, this
Relative cratering rate
ANTHONY LAGAIN
Sky & Telescope - June 2024
Table of Contents for the Digital Edition of Sky & Telescope - June 2024
Contents
Sky & Telescope - June 2024 - Cover1
Sky & Telescope - June 2024 - Cover2
Sky & Telescope - June 2024 - 1
Sky & Telescope - June 2024 - Contents
Sky & Telescope - June 2024 - 3
Sky & Telescope - June 2024 - 4
Sky & Telescope - June 2024 - 5
Sky & Telescope - June 2024 - 6
Sky & Telescope - June 2024 - 7
Sky & Telescope - June 2024 - 8
Sky & Telescope - June 2024 - 9
Sky & Telescope - June 2024 - 10
Sky & Telescope - June 2024 - 11
Sky & Telescope - June 2024 - 12
Sky & Telescope - June 2024 - 13
Sky & Telescope - June 2024 - 14
Sky & Telescope - June 2024 - 15
Sky & Telescope - June 2024 - 16
Sky & Telescope - June 2024 - 17
Sky & Telescope - June 2024 - 18
Sky & Telescope - June 2024 - 19
Sky & Telescope - June 2024 - 20
Sky & Telescope - June 2024 - 21
Sky & Telescope - June 2024 - 22
Sky & Telescope - June 2024 - 23
Sky & Telescope - June 2024 - 24
Sky & Telescope - June 2024 - 25
Sky & Telescope - June 2024 - 26
Sky & Telescope - June 2024 - 27
Sky & Telescope - June 2024 - 28
Sky & Telescope - June 2024 - 29
Sky & Telescope - June 2024 - 30
Sky & Telescope - June 2024 - 31
Sky & Telescope - June 2024 - 32
Sky & Telescope - June 2024 - 33
Sky & Telescope - June 2024 - 34
Sky & Telescope - June 2024 - 35
Sky & Telescope - June 2024 - 36
Sky & Telescope - June 2024 - 37
Sky & Telescope - June 2024 - 38
Sky & Telescope - June 2024 - 39
Sky & Telescope - June 2024 - 40
Sky & Telescope - June 2024 - 41
Sky & Telescope - June 2024 - 42
Sky & Telescope - June 2024 - 43
Sky & Telescope - June 2024 - 44
Sky & Telescope - June 2024 - 45
Sky & Telescope - June 2024 - 46
Sky & Telescope - June 2024 - 47
Sky & Telescope - June 2024 - 48
Sky & Telescope - June 2024 - 49
Sky & Telescope - June 2024 - 50
Sky & Telescope - June 2024 - 51
Sky & Telescope - June 2024 - 52
Sky & Telescope - June 2024 - 53
Sky & Telescope - June 2024 - 54
Sky & Telescope - June 2024 - 55
Sky & Telescope - June 2024 - 56
Sky & Telescope - June 2024 - 57
Sky & Telescope - June 2024 - 58
Sky & Telescope - June 2024 - 59
Sky & Telescope - June 2024 - 60
Sky & Telescope - June 2024 - 61
Sky & Telescope - June 2024 - 62
Sky & Telescope - June 2024 - 63
Sky & Telescope - June 2024 - 64
Sky & Telescope - June 2024 - 65
Sky & Telescope - June 2024 - 66
Sky & Telescope - June 2024 - 67
Sky & Telescope - June 2024 - 68
Sky & Telescope - June 2024 - 69
Sky & Telescope - June 2024 - 70
Sky & Telescope - June 2024 - 71
Sky & Telescope - June 2024 - 72
Sky & Telescope - June 2024 - 73
Sky & Telescope - June 2024 - 74
Sky & Telescope - June 2024 - 75
Sky & Telescope - June 2024 - 76
Sky & Telescope - June 2024 - 77
Sky & Telescope - June 2024 - 78
Sky & Telescope - June 2024 - 79
Sky & Telescope - June 2024 - 80
Sky & Telescope - June 2024 - 81
Sky & Telescope - June 2024 - 82
Sky & Telescope - June 2024 - 83
Sky & Telescope - June 2024 - 84
Sky & Telescope - June 2024 - Cover3
Sky & Telescope - June 2024 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202411
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com