Sky & Telescope - February 2021 - 8

NEWS NOTES

Spacecraft Takes a Bite of Asteroid Bennu

IN BRIEF

CHEERS ERUPTED in the control room

In preparation for OSIRIS-REX's sampling
maneuver on Bennu, the mission team
mapped the surface at a resolution down
to 5 cm (2 inches) per pixel. Besides enabling a safe landing, the images revealed
unexpected properties of Bennu's surface.
Daniella DellaGiustina (University of Arizona) and colleagues report September 21st
in Nature Astronomy six anomalously
bright, large boulders that stand out from
the rest of the much darker surface. The
rocks' compositions indicate their likely origin on another asteroid: 4 Vesta. Perhaps
Bennu picked them up as it wandered
through the asteroid belt to its present
trajectory inside Mars's orbit. The images
also showed reflective patches on some
otherwise-dark boulders, which caught the
eye of Hannah Kaplan (NASA Goddard)
and colleagues. They found that the bright
spots are rich in carbonates, particularly
calcite, a highly reflective form of calcium
carbonate. In the October 8th Science,
Kaplan and colleagues make the case that
these veins of minerals precipitated out of
hot water flowing through cracks deep inside a young planetesimal. Bennu is likely
a chip off that planetesimal block, formed
from the debris of a catastrophic collision
about 1 billion years ago.
„ JEFF HECHT

on October 20th as NASA's OSIRISREX mission successfully " tagged " the
diamond-shape asteroid 101955 Bennu.
The spacecraft's touch-and-go sample acquisition mechanism (TAGSAM)
dug its head up to 48 cm (19 inches)
into the regolith, puffed nitrogen gas
to stir up and capture surface material,
and reared away.
Just approaching the boulder-strewn
surface was a feat for the OSIRIS-REX
team: The surface was much rougher
than expected, and the team took extra
time to select a landing site. As it flew
in, the spacecraft first had to slip past
a two-story-high boulder nicknamed
" Mount Doom " before targeting a clear
slot about the width of two parking
spots. The mission was 18.5 lightminutes from Earth, so the spacecraft
navigated the approach on its own.
Though the final landing target was
much smaller than the mission's initial
25-meter-radius requirement, OSIRISREX touched the surface within a meter
of where it was supposed to land.
T OSIRIS-REX's sampling arm contacts Bennu.

The day after collection, the mission team imaged the TAGSAM to
confirm success. In fact, the maneuver was almost too successful: The
sample overflowed the head as multiple large rocks wedged open a Mylar
flap and allowed some smaller grains
to escape. The team acted quickly,
using the TAGSAM arm to place the
precious cargo in the return capsule
on October 27th.
Immediately stowing the sample
meant forgoing a spin test, which
would have " weighed " the collection by measuring the spacecraft's
moment of inertia and comparing
it to a baseline obtained before the
touch-and-go maneuver. Nevertheless, calculations showed the collected mass exceeded expectations:
The team estimates the asteroid
encounter filled the TAGSAM head
with 258 to 575 grams (0.56 to
1.26 lb) of material - well above the
minimum target of 60 grams set for
the mission. It appears only a small
fraction of this was lost due to the
open Mylar flap.
Although the sampling phase is
complete, OSIRIS-REX won't begin
its return to Earth until March 2021,
and the return trip will take some
time: The flyby and sample drop-off
is expected on September 24, 2023.
Once collected from the landing site
in the Utah Test and Training Range,
the sample will be divided: a quarter
will go to the mission's science team
and 4% to partners at the Canadian Space Agency. Another 0.5%
will go to the Japanese Aerospace
Exploration Agency in exchange for
pieces of the asteroid 162173 Ryugu,
which JAXA's Hayabusa 2 mission
will drop off during an Earth flyby
in December 2020 (S&T: June 2019,
p. 10). The remainder of the sample
will be preserved, available to future
researchers worldwide as investigative technologies advance.
„ DAVID DICKINSON

8

FEBRUARY 2 021 * SK Y & TELESCOPE

Bennu's Surface Surprises

Read more about findings on Bennu's
surface at https://is.gd/BennuVesta.

COSMOLOGY

Astronomers Chart History
of Star Formation
A HISTORICAL RECORD of molecular
hydrogen gas - the stuff that makes
stars - provides astronomers with a
sweeping survey of star formation, as
well as a prediction for when the universe's stars will go dark.
Astronomers have already charted
the rise and fall of galaxies' star formation over time, revealing a stellar baby
boom that peaked about 10 billion
years ago; rates have been decreasing
ever since. To explore these trends,
astronomers went a step earlier in the
process, tracking not just the stars born
but the material used to make them.

N ASA / GODDA RD / UNIV ERSIT Y OF A RIZON A

ASTEROIDS


https://www.is.gd/BennuVesta

Sky & Telescope - February 2021

Table of Contents for the Digital Edition of Sky & Telescope - February 2021

Contents
Sky & Telescope - February 2021 - Cover1
Sky & Telescope - February 2021 - Cover2
Sky & Telescope - February 2021 - 1
Sky & Telescope - February 2021 - Contents
Sky & Telescope - February 2021 - 3
Sky & Telescope - February 2021 - 4
Sky & Telescope - February 2021 - 5
Sky & Telescope - February 2021 - 6
Sky & Telescope - February 2021 - 7
Sky & Telescope - February 2021 - 8
Sky & Telescope - February 2021 - 9
Sky & Telescope - February 2021 - 10
Sky & Telescope - February 2021 - 11
Sky & Telescope - February 2021 - 12
Sky & Telescope - February 2021 - 13
Sky & Telescope - February 2021 - 14
Sky & Telescope - February 2021 - 15
Sky & Telescope - February 2021 - 16
Sky & Telescope - February 2021 - 17
Sky & Telescope - February 2021 - 18
Sky & Telescope - February 2021 - 19
Sky & Telescope - February 2021 - 20
Sky & Telescope - February 2021 - 21
Sky & Telescope - February 2021 - 22
Sky & Telescope - February 2021 - 23
Sky & Telescope - February 2021 - 24
Sky & Telescope - February 2021 - 25
Sky & Telescope - February 2021 - 26
Sky & Telescope - February 2021 - 27
Sky & Telescope - February 2021 - 28
Sky & Telescope - February 2021 - 29
Sky & Telescope - February 2021 - 30
Sky & Telescope - February 2021 - 31
Sky & Telescope - February 2021 - 32
Sky & Telescope - February 2021 - 33
Sky & Telescope - February 2021 - 34
Sky & Telescope - February 2021 - 35
Sky & Telescope - February 2021 - 36
Sky & Telescope - February 2021 - 37
Sky & Telescope - February 2021 - 38
Sky & Telescope - February 2021 - 39
Sky & Telescope - February 2021 - 40
Sky & Telescope - February 2021 - 41
Sky & Telescope - February 2021 - 42
Sky & Telescope - February 2021 - 43
Sky & Telescope - February 2021 - 44
Sky & Telescope - February 2021 - 45
Sky & Telescope - February 2021 - 46
Sky & Telescope - February 2021 - 47
Sky & Telescope - February 2021 - 48
Sky & Telescope - February 2021 - 49
Sky & Telescope - February 2021 - 50
Sky & Telescope - February 2021 - 51
Sky & Telescope - February 2021 - 52
Sky & Telescope - February 2021 - 53
Sky & Telescope - February 2021 - 54
Sky & Telescope - February 2021 - 55
Sky & Telescope - February 2021 - 56
Sky & Telescope - February 2021 - 57
Sky & Telescope - February 2021 - 58
Sky & Telescope - February 2021 - 59
Sky & Telescope - February 2021 - 60
Sky & Telescope - February 2021 - 61
Sky & Telescope - February 2021 - 62
Sky & Telescope - February 2021 - 63
Sky & Telescope - February 2021 - 64
Sky & Telescope - February 2021 - 65
Sky & Telescope - February 2021 - 66
Sky & Telescope - February 2021 - 67
Sky & Telescope - February 2021 - 68
Sky & Telescope - February 2021 - 69
Sky & Telescope - February 2021 - 70
Sky & Telescope - February 2021 - 71
Sky & Telescope - February 2021 - 72
Sky & Telescope - February 2021 - 73
Sky & Telescope - February 2021 - 74
Sky & Telescope - February 2021 - 75
Sky & Telescope - February 2021 - 76
Sky & Telescope - February 2021 - 77
Sky & Telescope - February 2021 - 78
Sky & Telescope - February 2021 - 79
Sky & Telescope - February 2021 - 80
Sky & Telescope - February 2021 - 81
Sky & Telescope - February 2021 - 82
Sky & Telescope - February 2021 - 83
Sky & Telescope - February 2021 - 84
Sky & Telescope - February 2021 - Cover3
Sky & Telescope - February 2021 - Cover4
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