Latest / Space News Today / MAVEN’s Silence: Unravelling the Mystery of Mars’ Lost Contact

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MAVEN’s Silence: Unravelling the Mystery of Mars’ Lost Contact · Space News Today

0:00
This is Spacetime series 28, episode 147
0:03
for broadcast on the 15th of December,
0:06
2025.
0:07
Coming up on Spaceime, NASA loses
0:10
contact with its maven Mars Orbiter. How
0:13
the cosmic landscape impacts the
0:15
galaxy's life cycle, and a new study
0:18
suggests the planets Uranus and Neptune
0:21
might be rock giants rather than ice
0:23
giants. All that and more coming up on
0:27
Spaceime.
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Welcome to Space Time with Stuart Garry.
0:48
NASA has lost contact with its Mars
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Atmosphere and Volatile Evolution or
0:52
Maven spacecraft. The agency says the
0:55
probe disappeared off the proverbial
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screens on December the 6th. At the
1:00
time, telemetry showed Maven was working
1:02
nominally as it passed behind Mars as
1:04
seen from Earth, but the spacecraft
1:07
didn't resume communications after
1:09
emerging from behind the planet. Mission
1:11
managers are now investigating the
1:13
anomaly and are yet to determine what's
1:15
gone wrong. The orbit has been circling
1:17
the red planet for more than a decade,
1:19
gathering scientific data and serving as
1:22
a key communications relay satellite.
1:25
Maven launched back in November 2013 and
1:28
entered orbit around Mars in September
1:30
2014. The spacecraft's primary mission
1:33
has been to study the planet's upper
1:35
atmosphere and interactions with the
1:37
solar wind, including how the atmosphere
1:40
escapes into space, helping scientists
1:42
better understand how the red planet
1:44
changed from a warm, wet world with a
1:46
thick atmosphere, one capable of
1:48
supporting liquid water on its surface
1:50
and turning it into the inhospitable,
1:52
freeze-dried desert it is today. This
1:55
report from NASA TV. Today, Mars is a
1:59
cold, dry world with a tenuous
2:01
atmosphere only 1% as thick as Earth's.
2:05
But in the ancient past, water flowed
2:07
freely across the Martian surface,
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maintained by a thick, early atmosphere.
2:13
Since it first arrived at the red planet
2:15
in September 2014, NASA's Maven
2:17
spacecraft has been studying how that
2:20
atmosphere was lost to space and with
2:22
it, the water.
2:26
In 2015, Maven observed the solar wind
2:29
eroding the Martian atmosphere. The
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solar wind is a stream of electrically
2:34
charged particles blowing from the sun.
2:36
Maven watched as ions from the Mars
2:39
upper atmosphere were accelerated by the
2:41
solar winds magnetic field and driven
2:43
into space, confirming that this process
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has deeply eroded the Martian
2:47
atmosphere.
2:49
In 2017, Maven showed that a process
2:52
called sputtering has had an even
2:54
greater effect on the atmosphere. When
2:56
ions from Mars get picked up by the
2:58
solar winds magnetic field, they can
3:00
crash into neutral atoms at the top of
3:02
the atmosphere, sputtering them into
3:04
space. Maven measured present-day
3:06
isotopes of argon, which can be removed
3:09
only by sputtering, to determine that
3:11
65% of the noble gas has been lost over
3:14
time. This allowed scientists to
3:16
estimate the escape of other gases, and
3:18
determine that sputtering has been the
3:20
primary mechanism driving the atmosphere
3:22
into space. Later in 2017, Maven
3:25
revealed a twist in Mars' invisible
3:28
magnetic tail. When the sun's magnetic
3:30
fields reach Mars, they pile up and wrap
3:33
around the planet, creating an induced
3:35
magnetic field that is drawn out behind
3:37
Mars like a comet's tail. The Martian
3:40
crust also contains small pockets of its
3:43
own early magnetic field, which rotate
3:45
along with the planet. Maven discovered
3:47
that when these two fields interact,
3:49
they put a twist in the magneto tail,
3:51
confirming model predictions.
3:54
In 2018, a runaway series of dust storms
3:57
created a dust cloud so large that it
3:59
enveloped the planet. During this global
4:02
dust storm, Maven observed an abrupt
4:04
unexpected spike in the amount of water
4:06
in the upper atmosphere. It discovered
4:09
that heating from dust storms can loft
4:11
water molecules far higher into the
4:13
atmosphere than usual, leading to a
4:15
sudden surge in water lost to space.
4:19
Later in 2018, Maven announced the
4:21
discovery of a new type of aurora at
4:23
Mars. The mission had previously
4:25
observed auroras during solar storms
4:28
after electrons from the sun struck the
4:30
upper atmosphere, causing it to glow
4:32
with ultraviolet light. Maven's 2018
4:35
discovery was the first observation of a
4:38
Mars proton aurora. When protons from
4:40
the solar wind pick up electrons from
4:42
the Martian ionosphere, they can slip
4:45
through the planet's bow shock and
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plunge into its upper atmosphere,
4:48
causing widespread auroras. On Earth,
4:52
proton auroras are isolated near the
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poles, but on Mars, they can bathe the
4:56
dayside in ultraviolet radiation.
5:00
In 2019, Maven produced the first map of
5:03
wind currents in the Martian
5:04
thermosphere, revealing disturbances and
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high altitude winds caused by terrain
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features on the surface. Maven sensed
5:11
these disturbances as it skimmed through
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the upper atmosphere, feeling the
5:16
imprint of mountains and valleys far
5:18
below.
5:19
In 2020, data for Maven led to the
5:22
creation of another new map showing the
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Martian atmosphere's electric current
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systems for the first time. Maven
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detected these currents indirectly by
5:30
observing the solar winds magnetic field
5:32
lines drape around the planet. Mapping
5:35
the electric current systems can help
5:37
scientists to better understand the
5:38
forces that drive atmospheric escape.
5:42
In 2022, Maven watched as the solar wind
5:45
unexpectedly disappeared from Mars. The
5:48
event occurred when a fastmoving patch
5:50
of the solar wind overtook a slower
5:52
moving region, leaving a void in its
5:54
wake. In response, the Martian
5:57
magnetosphere ballooned outward by
5:59
thousands of kilome, engulfing Maven's
6:01
orbit and causing the solar wind to
6:03
temporarily disappear from view. In 2022
6:07
and 2023, Maven captured stunning
6:09
ultraviolet images of Mars when the
6:11
planet was near opposite ends of its
6:13
elliptical orbit. The first image was
6:16
taken when the southern hemisphere was
6:17
in summer, which coincides with Mars's
6:20
closest approach to the sun. Canyons and
6:22
basins are covered with a thin haze of
6:25
ozone indicated by a tinge of pink. The
6:28
second image was taken during northern
6:30
spring after Mars had passed its
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furthest point from the sun. White
6:34
clouds hint at rapidly changing
6:36
conditions in the northern polar regions
6:38
while deep magenta signals a buildup of
6:41
ozone during the frigid winter.
6:44
In 2024, Maven observed the aftermath of
6:47
an ex-class solar flare, the strongest
6:49
type of eruption from the sun. The flare
6:52
was quickly followed by a burst of
6:54
charged particles crashing into Mars,
6:56
leaving black and white streaks on
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images taken by NASA's Curiosity rover.
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Maven watched from above as auroras lit
7:04
up the planet in a brilliant display of
7:06
celestial fireworks.
7:09
Maven's other role as a communications
7:12
relay satellite has provided a key link
7:14
between both the Mars Curiosity and Mars
7:16
Perseverance rovers down on the Martian
7:18
surface and mission managers at the Jet
7:21
Propulsion Laboratory in Pasadena,
7:22
California by way of NASA's Deep Space
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Communications Network ground stations
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in Goldstone, California, Madrid, Spain,
7:30
and Camber, Australia. NASA's Mars
7:33
Odyssey spacecraft and Mars
7:35
Reconnaissance Orbiter also serve as
7:37
communications relays for the rovers,
7:39
but both are significantly older than
7:41
Maven. And this isn't the first time
7:44
that Maven has suffered technical
7:46
issues. Back in 2022, the prob's
7:49
inertial measurement units, which are
7:51
used for navigation, failed. That force
7:53
mission manages to switch the orbiter to
7:55
a stellar navigation system, minimizing
7:58
reliance on the inertial measurement
7:59
units. Maven has enough propellant to
8:02
maintain its orbit through at least
8:04
until the end of the decade.
8:06
This is spaceime still to come. How a
8:10
cosmic landscape can impact the galaxy's
8:12
life cycle. And a new study suggests the
8:15
solar systems two ice giants, Uranus and
8:18
Neptune, might actually be more rocky
8:20
than icy. All that and more still to
8:22
come on Spaceime.
8:39
A new study has shown how a galaxy's
8:41
neighborhood can influence its
8:43
evolution. The findings reported in the
8:45
monthly notices of the Royal
8:47
Astronomical Society offers a new level
8:49
of detail into science's understanding
8:51
of galactic evolution in the distant
8:53
universe. The research is based on data
8:56
from Devils, the Deep Extragalactic
8:58
Visible Legacy Survey, an extensive
9:01
galaxy evolution survey which shows that
9:03
a galaxy's local environment plays a
9:05
major role in how it changes over time,
9:08
strongly influencing its shape, size,
9:11
and even its growth rate. The survey
9:13
combines data from a wide range of
9:15
terrestrial and space-based telescopes
9:17
to investigate various aspects of
9:19
astrophysics for analyzing hundreds of
9:21
thousands of galaxies. The project lead,
9:24
Luke Davies, from the University of
9:26
Western Australia, node of the
9:28
International Center for Radioastronomy
9:30
Research, says the Devil Survey is
9:32
unique in that it's the first of its
9:34
kind to explore detailed aspects of the
9:36
distant universe. It focuses on galaxies
9:39
that existed up to 5 billion years ago
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and examines how these galaxies have
9:44
changed through to the present day. He
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says, "While previous surveys during
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this period of universal history have
9:51
explored the broad evolution of galaxy
9:53
properties, they've inherently lacked
9:54
the capacity to determine the finer
9:56
details of the cosmic landscape. The
9:59
Devil Survey has allowed astronomers to
10:01
zoom in and focus on mapping out the
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small scale environment of galaxies.
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This new approach has allowed Davies and
10:08
colleagues to identify the number of
10:10
stars in a galaxy, understand ongoing
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star formation, and analyze their visual
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appearance, shapes, and structures. They
10:18
can then compare these properties
10:19
between galaxies in the present day
10:21
universe with galaxies that existed
10:23
around 5 billion years ago. In order to
10:25
determine how galaxies have changed over
10:28
time, they found that galaxies that are
10:30
surrounded by lots of other galaxies,
10:32
one might say the bustling centers of
10:34
galactic cities in the cosmos tend to
10:36
grow more slowly and have different
10:38
structures compared to their more
10:40
isolated counterparts. In crowded
10:42
regions of the universe, galaxies
10:44
interact with each other and compete for
10:46
resources such as gas to form new stars
10:48
and grow. Davy says this competition can
10:52
impact their evolution and in some
10:54
instances cause star formation to slow
10:56
down earlier than expected causing
10:58
galaxies to die.
10:59
>> It's a survey that's primarily based
11:02
around observations which are done with
11:04
the Anglo Australian telescope in New
11:06
South Wales. So what we do is we pick a
11:08
few patches of the night sky and we take
11:11
a lot of imaging data that currently
11:12
exists in those regions and we put it
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together to build a sample of galaxies
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that we want to explore. And then we go
11:17
to the Anglo Australian telescope and we
11:19
measure spectra for all of those
11:21
galaxies. And what that primarily allows
11:23
us to do is to measure the
11:25
three-dimensional structure of the
11:27
universe. So we map out the distances
11:29
and the positions of all of the
11:30
galaxies. And then we determine what the
11:32
structure looks like. And we use that
11:33
structure to work out places in the
11:35
universe where there are lots of
11:36
galaxies. So very sort of overdense
11:39
regions which are your sort of bustling
11:40
city centers of of the universe
11:42
environment. So they're mostly galaxy
11:44
groups which are slightly smaller than
11:46
clusters. So given the volume Yeah.
11:49
Yeah. So sort of from the local group
11:50
size up to a little bit bigger mainly
11:52
because of the volumes that we probe are
11:54
quite small in comparison to the nearby
11:56
universe. So you actually don't get some
11:58
of the really massive cluster type
12:00
things. Then what we do is we try and
12:02
combine all the information about what
12:04
the galaxy's local environment is like.
12:06
So how how clustered the regions are and
12:08
link that up with the properties of the
12:10
galaxies to see how where they live is
12:12
impacting their life cycle.
12:14
>> And what have you found?
12:15
>> What we found is that when you start to
12:17
to map out the universe on this sort of
12:20
smallalish scale in terms of
12:22
environments that the properties of
12:23
galaxies are very strongly linked to
12:25
where they live in the universe. So if
12:27
you grow up in bustling sort of city
12:29
centers of the the the galactic
12:31
environment. You actually die more
12:32
easily. Um you form less stars. you you
12:35
look different. You grow in a different
12:37
way to if you live in a sort of isolated
12:39
remote region of space.
12:41
>> I would have thought that if you're in a
12:42
busy bustling area with lots of other
12:44
galaxies, it'd be easier to steal gas
12:46
from them and make more stars and even
12:49
grow bigger because you can merge with
12:51
them. That's not what you found. But
12:52
>> so so that's largely true for the the
12:55
sort of big central galaxies in those
12:57
environments. We tend to split galaxies
12:59
in those environments to centrals and
13:01
satellites where central is sort of the
13:03
main big galaxy in the middle and the
13:04
satellites are all the other ones which
13:06
are moving moving around it. So for the
13:08
central region being in that over dense
13:10
environment actually helps it to grow
13:11
more massive but for the satellites it
13:13
actually stops them from forming new
13:15
stars so that they don't grow any bigger
13:17
and all of those interactions with the
13:20
other galaxies actually change the way
13:21
the galaxy looks as well. So, we define
13:24
how a galaxy looks at something called
13:25
morphology, which basically defines
13:27
whether it's sort of a big blobby red
13:29
structure or a disc-like spiral
13:31
structure. And where a galaxy lives in
13:33
its environment and its interactions
13:35
with other galaxies changes the type of
13:37
morphology that that galaxy is.
13:38
>> Is that why the large and small melanic
13:41
clouds are disrupted spirals or
13:43
irregular spirals rather than grand
13:45
spirals like say the Milky Way or
13:47
>> Yeah. So, they're also much smaller. So
13:49
these sort of smaller regular galaxies
13:51
tend to form as more sort of blobby
13:53
structures but yeah their interactions
13:54
with the Milky Way will make them look
13:56
different. So imagine if you have like
13:58
say you have two big spiralally type
14:00
galaxies and you smash them both
14:01
together you end up with something that
14:03
looks more like an elliptical galaxy and
14:04
because those processes are happening
14:06
more readily in group environments you
14:08
end up getting more elliptical like
14:10
things in group environments than you
14:12
would in isolated environments. The real
14:14
benefit of what we've done with devils
14:16
in this is that this type of science of
14:18
mapping out the sort of group scale, so
14:20
the the much lower mass scale than
14:22
clusters environments has only
14:23
previously been done in the relatively
14:25
local universe. The reason for this is
14:27
that to be able to map out the
14:28
three-dimensional structure of a
14:30
universe, you need to measure red shifts
14:32
basically for lots of galaxies to get to
14:33
their distance. And doing that outside
14:35
of the local universe is really
14:36
problematic because you have to observe
14:38
for a really long time to get enough
14:40
signal to noise to measure the red
14:41
shift. So we've done this in the local
14:43
universe with other surveys, but with
14:44
Devils, what we've done is we've
14:46
stretched that out into the much more
14:48
distant universe by observing the same
14:49
galaxy for much longer time basically to
14:52
get their red shift. So it's the first
14:53
time we've really managed to map out
14:54
this sort of group scale structure in
14:56
the very distant universe
14:58
>> and you're moving from devils to waves
15:00
next.
15:01
>> Yeah. So waves is a survey that going to
15:03
be starting next year on a on a new
15:05
facility which is called foremost which
15:07
is the 4 m multiobject spectrograph
15:10
telescope which is in Chile. And what
15:11
we're doing with waves is that we
15:13
actually have a few different sort of
15:15
surveys that we're doing but one of the
15:16
components of waves which is called
15:18
waves deep. It's basically the same as
15:19
devils but over a much much larger area.
15:22
So essentially we'll be doing all of the
15:23
science that we can do with devils now
15:25
but to a much much finer degree over
15:27
much larger volumes of the universe. We
15:29
actually um have got the first test
15:31
observations from foremost for some of
15:33
the galaxies in waves which has been
15:35
really exciting. So, we've all been
15:36
working away to try and understand
15:38
everything that's going on with the
15:39
telescope and then we'll start waves in
15:40
Earth next year.
15:41
>> One of the big topics of recent papers
15:44
that I've seen has been this ongoing
15:46
hypothesis that the Milky Way may not be
15:50
within a a strand of galaxies in the
15:53
cosmic web of the universe, but rather
15:56
it may actually be at or near the edge
15:58
of a large void. Has your work in any
16:00
way at all helped resolve that issue?
16:02
The issue of this is is that some of our
16:05
our results in terms of our cosmological
16:08
analyses, so analyses of how the whole
16:10
universe works essentially and how the
16:12
whole universe is evolving are a little
16:13
bit in tension with each other. And one
16:15
of the possible solutions for that is
16:16
that we live in a slightly atypical part
16:19
of the universe. So next to a cosmic
16:21
void which would mean that some of our
16:22
our measurements that we use to infer
16:24
cosmological principles are a little bit
16:26
wrong because all of those assume
16:28
basically that we live in a very
16:30
representative place in the universe.
16:32
Now it is really super interesting but
16:34
it's not really something that I I work
16:36
on massively. I look at galaxies which
16:38
are much much further away than that
16:40
local volume. But there is an
16:42
Australian-led survey that's going to be
16:44
happening on for almost as well called
16:45
the 4HS which is being run from the
16:48
country which will actually test some of
16:49
these things about the distribution of
16:50
galaxies in the very local universe as
16:52
well. So I would say hold tight and in
16:55
sort of four or five years time when we
16:56
have results from foremost we might be
16:58
able to say something a bit more about
16:59
this problem.
17:00
>> The reason for this assumption that
17:02
we're in a of the edge of a void is
17:04
simply because of studies looking at
17:06
expansion of the universe based on dark
17:08
energy.
17:08
>> Yeah. So that's one of the cosmological
17:11
measurements that I mentioned. So there
17:12
there's currently just this tension as
17:14
to how dark energy is evolving and
17:17
whether it's changing with time or
17:18
whether it's a constant. And one of the
17:20
potential solutions to all of this
17:21
conflict is that we live within this
17:23
void which actually allows you to match
17:25
up some of the sort of slightly
17:27
disperate observations that you get from
17:28
doing different measurements.
17:29
>> Yeah, it's a small void if it is a void.
17:31
But uh
17:32
>> the interesting thing is of course there
17:34
have been some new results that have
17:35
just come out showing that dark energy
17:37
isn't constant but in fact we have not
17:40
just reached the maximum extent of dark
17:42
energy but it may be going in reverse
17:44
now.
17:45
>> Yes. So most of those results are coming
17:47
out of a surveill called DESI which is
17:49
done in the the northern hemisphere and
17:52
not to bang on about foremost too much
17:54
as a pretty amazing instrument when it
17:56
starts going but there's also a
17:57
different survey that's going to be done
17:58
on foremost which is a survey which is
18:00
similar to DESI but will be in the
18:02
southern hemisphere. So when that's done
18:04
combining the data from DESI and this
18:06
foremost survey in the southern
18:08
hemisphere will actually produce way
18:09
better constraints on all of these
18:11
measurements. So it's quite exciting
18:12
that we might have sort of desi times
18:15
two in about five years time where we
18:16
get much better constraints on all of
18:18
this and we'll probably then get a
18:19
definitive answer on to whether dark
18:21
energy is changing with time or is
18:23
constant.
18:23
>> That's associate professor Luke Davies
18:26
from the University of Western Australia
18:28
node of the international center for
18:29
radioastronomy research and this is
18:33
spacetime still to come. A new study
18:36
suggests the solar systems two ice giant
18:38
planets Uranus and Neptune may actually
18:40
be more rocky than icy. And later in the
18:43
science report, a new study warns
18:46
insufficient sleep may shorten your
18:48
lifespan. All that and more still to
18:50
come on Spaceime.
19:08
A new study suggests the solar systems
19:10
two ice giant planets, Uranus and
19:12
Neptune, might actually be more rocky
19:14
than icy. The findings follow new
19:17
computer simulations examining the
19:19
likely internal structures of the two
19:21
worlds. Now, this new study isn't
19:24
claiming that these two blue planets are
19:26
one type of the other, water or rock.
19:28
Rather, it simply challenges the idea
19:30
that ice rich isn't the only
19:32
possibility. This new interpretation is
19:35
also consistent with the discovery that
19:37
the dwarf planet Pluto is rock dominated
19:39
in its composition.
19:42
The planets in our solar system are
19:44
typically divided into three broad
19:46
categories based on their general
19:47
composition. There are the four
19:50
terrestrial rocky planets, Mercury,
19:52
Venus, Earth, and Mars. Then the two gas
19:55
giants, Jupiter, and Saturn. And
19:57
finally, the two ice giants, Uranus and
20:00
Neptune. Now, according to the new work
20:02
carried out by the University of Zurich
20:04
scientific team, Uranus and Neptune
20:06
might actually be more rocky than icy.
20:09
The study's lead author, Luca Morph,
20:11
says the ice giant classification might
20:13
be an oversimplification, but he admits
20:16
both worlds are still poorly understood
20:18
and models on the two based on physics
20:20
are too assumptionheavy, while imperial
20:22
models are too simplistic. Morphin
20:25
colleagues combined both approaches in
20:27
order to get internal models of the two
20:29
planets that are both agnostic and
20:31
physically consistent. Now to do this
20:34
they first started with random density
20:36
profiles for each planet's interior
20:38
based on a numerical framework. They
20:41
then calculated planetary gravitational
20:43
fields in a way that was consistent with
20:44
the observed data available and that
20:47
allowed them to infer a possible
20:48
internal composition. Finally, the
20:51
process is repeated to obtain the best
20:53
possible match between models and
20:55
observational data. And the authors
20:58
found that the potential internal
20:59
composition of the pair isn't limited to
21:02
mostly ices. Instead, a new range of
21:06
internal compositions show that both
21:08
planets can either be water-rich ice or
21:10
rockri material. The study has also
21:14
brought a new perspective on both Uranus
21:16
and Neptune's puzzling magnetic fields.
21:18
While the Earth has clear north and
21:20
south magnetic poles, the magnetic
21:22
fields of Uranus and Neptune are far
21:24
more complex and include more than just
21:26
two poles. The new models show ionic
21:29
water layers which generate magnetic
21:31
dynamos at locations that help explain
21:34
the observed nondipolar magnetic fields.
21:37
They also found that Uranus's magnetic
21:39
field originates far deeper inside the
21:42
planet than that of Neptune. While these
21:44
new results are promising, uncertainty
21:47
still remains. One of the main issues is
21:50
that physicists still barely understand
21:52
how materials behave under the exotic
21:54
conditions of pressure and temperature
21:56
which are found at the heart of a planet
21:58
and that will impact results. Still,
22:01
despite the uncertainties, these new
22:03
results are paving the way for new
22:05
potential interior composition
22:07
scenarios. scenarios which are
22:09
challenging decades old assumptions and
22:11
which could guide future research into
22:14
planetary conditions.
22:16
This is spacetime.
22:33
And time now to take a brief look at
22:35
some of the other stories making news in
22:37
science this week with a science report.
22:39
A new study warns insufficient sleep may
22:42
shorten your life. The findings reported
22:45
in the journal Sleep Advances compared
22:47
sleep patterns with life expectancy. And
22:50
the authors found that as a behavioral
22:52
driver for life expectancy, sleep stood
22:55
out far more than diet, exercise,
22:58
loneliness, and indeed more than any
23:00
other factor except smoking. For the
23:02
study, the CDC, the Centers for Disease
23:05
Control and Prevention, defined
23:07
sufficient sleep as at least 7 hours per
23:09
night, which is recommended by the
23:11
American Academy of Sleep Medicine and
23:13
by the Sleep Research Society. Although
23:15
previous research has shown broadly that
23:17
a lack of adequate sleep does lead to
23:19
high mortality risk, the new research is
23:22
the first to reveal year-to-year
23:24
correlations between sleep and life
23:26
expectancy.
23:28
The World Meteorological Organization
23:30
says there's now a 55% chance of a weak
23:33
leninia weather pattern developing over
23:35
the next 3 months. Leninia conditions
23:38
typically bring higher rainfall and
23:40
cooler temperatures across Australia.
23:42
And the study's authors say climate has
23:45
been at borderline leninia conditions
23:47
since mid- November. The agency says
23:49
Leninia is just one of the climatic
23:51
patterns influencing our weather with
23:53
climate change also having a major
23:55
impact on temperatures and extreme
23:57
weather events.
24:00
One of the longest and most intact
24:02
segments of Jerusalem's city wall has
24:04
been uncovered by archaeologists with
24:06
the Israeli Antiquities Authority. The
24:09
remarkably well preserved segment dates
24:11
back to the Hassamean Makabe period of
24:13
the late 2nd century B.C.E. Some 200
24:17
years before Christ and 800 years before
24:20
the birth of Islam, the ancient Jewish
24:22
fortification was unearthed within the
24:24
Kishel complex at the Tower of David
24:27
adjacent to the historic citadel. The
24:29
newly uncovered segment is over 40 m
24:32
long and some 5 m wide. It was built
24:35
from massive stone blocks that were
24:37
finally dressed with a distinctive
24:38
chiseled boss typical of the Himmonian
24:40
period. The authors believe the wall
24:43
originally stood over 10 m high. Similar
24:47
sections of the defensive system have
24:48
been uncovered around Mount Zion, the
24:50
city of David, the courtyard of the
24:52
citadel, and along parts of the western
24:54
boundary of Jerusalem, but none are as
24:57
extensive or as well preserved.
25:01
A new study by Noah, the National
25:03
Oceanic and Atmospheric Administration,
25:05
has debunked the idea that increases in
25:07
atmospheric carbon dioxide levels will
25:10
provide long-term improvements in plant
25:12
growth. Skeptics Tim Mendum says while
25:15
some increases in CO2 levels are
25:17
beneficial for plants, too much does end
25:20
up killing them.
25:21
>> There's a lot of people saying that
25:22
because we're putting out carbon dioxide
25:23
as part of our sort of energy activities
25:25
and that plants take in carbon dioxide
25:27
to help them grow. If it's a good thing
25:29
we're putting out the food that plants
25:30
use. That's actually to a certain
25:32
extent, a little extent, that's correct.
25:34
Plants do take on carbon dioxide. And
25:36
there can be times when they flourish in
25:38
certain environments, but the trouble is
25:39
you can have too much and plants can
25:41
only absorb so much in the same way as
25:43
the sea can only absorb so much. In
25:45
fact, it's the sea which is absorbing
25:47
most of the carbon dioxide that is
25:49
absorbed. So the trees can only take so
25:50
much they can bloom and blossom and then
25:52
after a while it'll start to kill them.
25:53
And then when it kills them, you get
25:54
drought. So you get less trees and that
25:56
sort of stuff. Also, of course, when a
25:57
plant dies, it gives up the carbon
25:59
dioxide it's taking in and storing,
26:01
especially for trees and things like
26:02
that. So, the argument that's being put
26:04
forward by a lot of people saying that
26:06
carbon dioxide is good for plants and
26:08
things and therefore we'll reforest
26:10
everything is wrong. And this has been
26:11
shown both in laboratory work and in
26:14
atmospheric work and satellite
26:15
photography. So, what will happen is
26:17
that plants will flourish and then die.
26:19
And when they die, you get drought, you
26:20
get low crop yield.
26:22
>> That's Tim Mendum from Australian
26:24
Skeptics.
26:40
and that's the show for now. Spacetime
26:43
is available every Monday, Wednesday,
26:44
and Friday through bites.com,
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Spacetime's also broadcast through the
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27:26
>> You've been listening to Spacetime with
27:28
Stuart Garry. This has been another
27:30
quality podcast production from
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byes.com.