- 4409
- LIFE - on
Mars and the farthest galaxy? - NASA's Perseverance rover may already have
found signs of life on Mars. The
discovery of an ancient lake bed beneath the Perseverance rover's location on
Mars could mean the robotic scout has already scraped up microbial fossils. But
we won't know for sure until we fetch the sample.
-
------------------------- 4409 - LIFE - on Mars and the farthest galaxy?
- “Perseverance” rover has found that Mars'
Jezero crater was at one point filled with water, offering a tantalizing hope
that it may have already unearthed fossilized life on the planet. The rover, which first touched down on the
crater in February 2021 along with its now-retired helicopter companion
“Ingenuity”, made the discovery using ground-penetrating radar revealing layers
of sediment once belonging to a lake that later dried into a gigantic delta.
-
- The finding raises hopes that, once
geological samples Perseverance has collected from the crater return to Earth,
researchers may find evidence that ancient life once thrived on the now
desiccated Red Planet.
-
- Perseverance rover is a key part of the
space agency's $2.7 billion Mars 2020 mission. Since it arrived on Mars, the
rover, alongside the older “Curiosity” rover, has been searching for signs of
ancient life on the Martian surface by trundling across the 30-mile Jezero
crater, collecting dozens of rock samples for eventual return to Earth.
-
- For three years, the rover was accompanied by the Ingenuity helicopter, which performed its 72nd and final flight over the Martian surface on January 18, 2024.
-
- The car-sized Perseverance is packed with
seven scientific instruments, one of which is the Radar Imager for Mars'
Subsurface Experiment (RIMFAX). By firing radar pings into the ground every 4
inches along its long and lonely journey, the rover built a map of pulses
reflected from depths of about 66 feet below the Martian crater’s surface.
-
- Now, this radar map has revealed the
existence of sediments that suggest the crater was once flooded with the waters
of a gigantic lake. Much like in drying lakes on Earth, its sediments were
transported by a river that formed a large delta, before later being deposited
and weathered by two distinct phases of erosion.
-
- The changes we see preserved in the rock
record are driven by large-scale changes in the Martian environment. We can see so much evidence of change in
such a small geographic area allowing us to extend our findings to the scale of
the entire crater.
-
- Since life on Earth is highly dependent on
water, evidence of water on Mars could be a vital clue that the planet was once
home to life, or, that life could still
be there. However, evidence for life on
the inhospitable neighboring planet has been elusive.
-
- To return Perserverance's precious cargo,
the Perseverance rover will await the arrival of the European Space Agency's
(ESA) planned Sample Retrieval Lander.
This is a spacecraft packaged with a small rocket that the rover will
load with its rock and soil samples before it is fired back into orbit.
-
- After being launched into space, the rocket
containing the sample will be collected by the ESA's Earth-return orbiter (ERO)
for a return flight to Earth. NASA initially planned for the ERO to launch
sometime in 2026, but this date has since been pushed back to 2028, meaning
that the sample will be back on Earth in 2033 at the earliest.
-
- In the meantime evidence for the first
generation of stars to exist in the universe has come to light. The proof is located in one of the most
distant galaxies known. The galaxy,
designated GN-z11, was discovered by the Hubble Space Telescope in 2015 and,
prior to the launch of the James Webb Space Telescope, it was considered the
most faraway galaxy known.
-
- With a redshift of 10.6, it makes more
sense to talk about how long ago it existed, rather than how far away it is.
That's because we see GN-z11 as it was just 430 million years after the Big
Bang due to the time it took for its light to travel to our corner of the
universe. For comparison, the universe today is 13.8 billion years old.
-
- GN-z11 is the most luminous galaxy known at
this particular redshift, and indeed this has become a common theme for high
redshift galaxies now almost regularly being found in the early universe by the
JWST. Many of them appear much brighter than what our models of galaxy
formation predict they should be. Those predictions are based on the “standard
model of cosmology”.
-
- The astronomers probed GN-z11 with the
JWST's two near-infrared instruments, the Near-Infrared Camera (NIRCam) and the
Near-Infrared Spectrometer (NIRSpec). They discovered evidence for the first
generation of stars, called Population III stars, as well as for a supermassive
black hole gobbling up huge amounts of matter and growing at a vastly
accelerated rate.
-
- Scientists can calculate the age of a star
based on its abundance of heavy elements, which would have been formed by
previous generations of stars that lived and died, spewing those heavy elements
into space where they ultimately get recycled in star-forming regions to form
new stellar bodies.
-
- The youngest stars that have formed during
the past five or six billion years are referred to as Population I stars, and
have the highest abundance of heavy elements. Our sun is a Population I star.
Older stars contain fewer heavy elements because there had been fewer
generations of stars before them. We call these Population II stars, and they
live in the oldest regions of our Milky Way galaxy.
-
- Population
III stars would have been the first stars to form, and because no other
stars came before them, they would have contained no heavy elements and be made
from only the pristine hydrogen and helium forged during the Big Bang. These
first stars are also thought to have been extremely luminous, with masses equal
to at least several hundred suns.
-
- Although astronomers still haven't seen
Population III stars directly they have detected indirect evidence for them in
GN-z11. NIRSpec observed a clump of ionized helium near the edge of GN-z11. The fact that we don't see anything else
beyond helium suggests that this clump must be fairly pristine.
-
- This is something that was expected by
theory and simulations in the vicinity of particularly massive galaxies from
these epochs that there should be pockets of pristine gas surviving in the
halo, and these may collapse and form Population III stars. This helium gas is being ionized by something
that's producing huge amounts of ultraviolet light, with that something
inferred as the Population III stars.
-
- Potentially, the helium witnessed is
leftover material from those stars' formation. The amount of ultraviolet light
required to ionize all that gas requires about 600,000 solar masses of stars in
total, shining with a combined luminosity 20 trillion times brighter than our
sun. These figures suggest distant galaxies such as GN-z11 would've been more
adept at forming massive stars than galaxies in the modern universe.
-
- The astronomers found evidence for a
two-million-solar-mass black hole at the heart of GN-z11.
Extremely dense gas that is common in the vicinity of supermassive black
holes accreting gas. These were the
first clear signatures that GN-z11 is hosting a black hole that is gobbling
matter.
-
- They also detected a powerful sleet of
radiation flowing off the accretion disk of matter swirling around the black
hole as well as ionized chemical elements typically found near accreting black holes.
-
- It is the most distant supermassive black
hole discovered so far and its gluttonous appetite leads to its accretion disk
becoming dense and hot, and shining brightly. This, combined with the
Population III stars, is what makes GN-z11 shine so brightly without breaking
standard cosmology,
-
-
March 28, 2023 LIFE
- on Mars and the farthest
galaxy? 4409
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------ “Jim Detrick” -----------
--------------------- --- Thursday, March 28,
2024
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