Sky & Telescope - December 2023 - 38

Interplanetary Sneezeguards
too. Even the magnetic field itself can dump energy into the
atmosphere, says Ofer Cohen (University of Massachusetts,
Lowell), if the space environment shakes the field up enough
to send waves through it in just the right way.
Against this onslaught, the magnetic field provides a limited
defense. The field only controls charged particles coming
in or going out, things like protons and ionized oxygen. It
cannot protect against radiation. Nor can it hold onto neutral
atoms and molecules. But planets larger than Mars are too
massive to let go of their neutral particles, which hunker
lower in the atmosphere, protected by gravity. For Venus and
Earth, ion-driven escape is the only option.
Even so, Earth's magnetosphere helps as much as it hurts.
In some cases, the field can spit energy from the solar wind
back out, but in others - particularly when the planet's field
and the solar wind's match up in just the right way - the
field stores the energy and deposits it in the atmosphere.
(Think aurorae.)
An intrinsic magnetosphere also makes the planet a much
larger target, diverting more energy from the solar wind into
the ionosphere. And the field funnels energy to specific regions
- on Earth, that's the poles - which can help heavier ions
escape. In fact, for our planet, the net effect may increase how
much energy the solar wind can dump into the atmosphere.
Simulations support this surprising conclusion. In 2018,
Herbert Gunell (now at UmeƄ University, Sweden) and others
explored what would happen to fictitious Venus, Earth, and
Mars analogs with different magnetic fields. They found that
the planets had similar loss rates whether unmagnetized or
strongly magnetized (as strongly as Jupiter, which has a field
20,000 times stronger than Earth's). But for fields similar to
the modern Earth's, the escape rate was a wee bit higher than
in the unmagnetized scenario.
Planetary Perm
Venus, Earth, and Mars all lose atmosphere differently. Earth
suffers a steady leak from its poles. At Venus, the atmospheric
loss looks more like your hair would if you stuck your head
out the car window while gunning it on the highway, Curry
says. And Mars has " party hair " - a big mohawk plume that
sometimes comes out of the pole and other times from closer
to the equator, depending on the orientation of the solar
wind's magnetic field.
The solar wind's properties matter a lot. The field it carries
is stronger at Venus's distance from the Sun (0.7 astronomical
unit) than it is at Earth (1 a.u.) or Mars (1.5 a.u.), and
it slicks Venus's atmospheric hair back as a result. (It's even
stronger at Mercury's roughly 0.38 a.u., but the pipsqueak
Iron Planet doesn't have an atmosphere.)
It's unclear how much Venus has suffered due to its
proximity to our star, but it has lost gas. Based on the ratio
of hydrogen to deuterium in its skies, we think nearly all of
the planet's water has fled to space. The likely reason is that
Venus was so hot under its greenhouse-gas blanket that the
water evaporated into the atmosphere, where sunlight could
break the molecules apart and leave the hydrogen atoms vulnerable
to space-weather robbery (S&T: Oct. 2021, p. 12).
" Escape has been really important at Venus, " Brain says.
Solar wind
Venus
SOLAR STYLIST Ions escape from Venus, Earth, and Mars in different
ways. At Venus, gas exits through a tail and a slick, pouf-like plume. At
Earth, tall polar fountains turn the planet into a garden gnome. And while
Mars loses three-quarters of its atmosphere through a tail, it also has a
tall plume, much larger than Venus's pouf when compared to the planet's
size. The plumes change latitude depending on the orientation of the solar
wind's magnetic field.
Earth
38 DECEMBER 2023 * SKY & TELESCOPE
BEATRIZ INGLESSIS / S&T

Sky & Telescope - December 2023

Table of Contents for the Digital Edition of Sky & Telescope - December 2023

Contents
Sky & Telescope - December 2023 - Cover1
Sky & Telescope - December 2023 - Cover2
Sky & Telescope - December 2023 - 1
Sky & Telescope - December 2023 - Contents
Sky & Telescope - December 2023 - 3
Sky & Telescope - December 2023 - 4
Sky & Telescope - December 2023 - 5
Sky & Telescope - December 2023 - 6
Sky & Telescope - December 2023 - 7
Sky & Telescope - December 2023 - 8
Sky & Telescope - December 2023 - 9
Sky & Telescope - December 2023 - 10
Sky & Telescope - December 2023 - 11
Sky & Telescope - December 2023 - 12
Sky & Telescope - December 2023 - 13
Sky & Telescope - December 2023 - 14
Sky & Telescope - December 2023 - 15
Sky & Telescope - December 2023 - 16
Sky & Telescope - December 2023 - 17
Sky & Telescope - December 2023 - 18
Sky & Telescope - December 2023 - 19
Sky & Telescope - December 2023 - 20
Sky & Telescope - December 2023 - 21
Sky & Telescope - December 2023 - 22
Sky & Telescope - December 2023 - 23
Sky & Telescope - December 2023 - 24
Sky & Telescope - December 2023 - 25
Sky & Telescope - December 2023 - 26
Sky & Telescope - December 2023 - 27
Sky & Telescope - December 2023 - 28
Sky & Telescope - December 2023 - 29
Sky & Telescope - December 2023 - 30
Sky & Telescope - December 2023 - 31
Sky & Telescope - December 2023 - 32
Sky & Telescope - December 2023 - 33
Sky & Telescope - December 2023 - 34
Sky & Telescope - December 2023 - 35
Sky & Telescope - December 2023 - 36
Sky & Telescope - December 2023 - 37
Sky & Telescope - December 2023 - 38
Sky & Telescope - December 2023 - 39
Sky & Telescope - December 2023 - 40
Sky & Telescope - December 2023 - 41
Sky & Telescope - December 2023 - 42
Sky & Telescope - December 2023 - 43
Sky & Telescope - December 2023 - 44
Sky & Telescope - December 2023 - 45
Sky & Telescope - December 2023 - 46
Sky & Telescope - December 2023 - 47
Sky & Telescope - December 2023 - 48
Sky & Telescope - December 2023 - 49
Sky & Telescope - December 2023 - 50
Sky & Telescope - December 2023 - 51
Sky & Telescope - December 2023 - 52
Sky & Telescope - December 2023 - 53
Sky & Telescope - December 2023 - 54
Sky & Telescope - December 2023 - 55
Sky & Telescope - December 2023 - 56
Sky & Telescope - December 2023 - 57
Sky & Telescope - December 2023 - 58
Sky & Telescope - December 2023 - 59
Sky & Telescope - December 2023 - 60
Sky & Telescope - December 2023 - 61
Sky & Telescope - December 2023 - 62
Sky & Telescope - December 2023 - 63
Sky & Telescope - December 2023 - 64
Sky & Telescope - December 2023 - 65
Sky & Telescope - December 2023 - 66
Sky & Telescope - December 2023 - 67
Sky & Telescope - December 2023 - 68
Sky & Telescope - December 2023 - 69
Sky & Telescope - December 2023 - 70
Sky & Telescope - December 2023 - 71
Sky & Telescope - December 2023 - 72
Sky & Telescope - December 2023 - 73
Sky & Telescope - December 2023 - 74
Sky & Telescope - December 2023 - 75
Sky & Telescope - December 2023 - 76
Sky & Telescope - December 2023 - 77
Sky & Telescope - December 2023 - 78
Sky & Telescope - December 2023 - 79
Sky & Telescope - December 2023 - 80
Sky & Telescope - December 2023 - 81
Sky & Telescope - December 2023 - 82
Sky & Telescope - December 2023 - 83
Sky & Telescope - December 2023 - 84
Sky & Telescope - December 2023 - Cover3
Sky & Telescope - December 2023 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202501
https://www.nxtbook.com/nxtbooks/aas/st_202412
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