- 4624 - MARS - had water at one time? A 4.45 billion-year-old crystal from Mars reveals the planet had water from the beginning. Water is ubiquitous on Earth, about 70% of Earth's surface is covered by water. Water is in the air, on the surface and inside rocks. Geologic evidence suggests water has been stable on Earth since about 4.3 billion years ago.
------------------------------------- 4624
- MARS - had
water at one time?
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- The history of water on early Mars is less
certain. Determining when water first appeared, where and for how long, are all
burning questions that drive Mars exploration. If Mars was once habitable, some
amount of water was required.
-
- We studied the mineral zircon in a meteorite
from Mars and found evidence that water was present when the zircon crystal
formed 4.45 billion years ago. This may
represent the oldest evidence for water on Mars.
-
- Water has long been recognized to have
played an important role in early Martian history. Like Earth, Mars formed
about 4.5 billion years ago. The history of Mars has four geological periods.
These are the Amazonian (from today back to 3 billion years), the Hesperian (3
billion to 3.7 billion years ago), the “Noachian” (3.7 billion to 4.1 billion
years ago) and the Pre-Noachian (4.1 billion to about 4.5 billion years ago).
-
- Evidence for water on Mars was first
reported in the 1970s when NASA's Mariner 9 spacecraft captured images of river
valleys on the Martian surface. Later orbital missions, including Mars Global
Surveyor and Mars Express, detected the widespread presence of hydrated clay
minerals on the surface. These would have needed water.
-
- The Martian river valleys and clay minerals
are mainly found in “Noachian terrains”, which cover about 45% of Mars. In
addition, orbiters also found large flood channels, outflow channels, in
Hesperian terrains. These suggest the short-lived presence of water on the
surface, perhaps from groundwater release.
-
- Most reports of water on Mars are in
materials or terrains older than 3 billion years. More recently than that,
there isn't much evidence for stable liquid water on Mars. But what about during the Pre-Noachian? When
did water first show up on Mars?
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- There are three ways to hunt for water on
Mars. The first is using observations of the surface made by orbiting
spacecraft. The second is using ground-based observations such as those taken
by Mars rovers. The third way is to
study Martian meteorites that have landed on Earth.
-
- The only Pre-Noachian material we have
available to study directly is found in meteorites from Mars. A small number of
all meteorites that have landed on Earth have come from our neighboring
planet. An even smaller subset of those
meteorites, believed to have been ejected from Mars during a single asteroid
impact, contain Pre-Noachian material.
-
- “Black Beauty” is a famous Martian
meteorite made up of broken-up surface material, or regolith. In addition to
rock fragments, it contains zircons that formed from 4.48 billion to 4.43
billion years ago. These are the oldest pieces of Mars known.
-
- While studying trace elements in one of
these ancient zircons we found evidence of hydrothermal processes, meaning they
were exposed to hot water when they formed in the distant past.
-
- The zircon being studied is 4.45 billion
years old. Within it, iron, aluminum and sodium are preserved in abundance
patterns like concentric layers, similar to an onion. This pattern, called oscillatory zoning,
indicates that incorporation of these elements into the zircon occurred during
its igneous history, in magma.
-
- The problem is that iron, aluminum and
sodium aren't normally found in crystalline igneous zircon. How did these elements end up in the Martian
zircon? The answer is hot water.
-
- In Earth rocks, finding zircon with growth
zoning patterns for elements like iron, aluminum and sodium is rare. One of the
only places where it has been described is from “Olympic Dam” in South
Australia, a giant copper, uranium and gold deposit.
-
- The metals in places like Olympic Dam were
concentrated by hydrothermal (hot water) systems moving through rocks during
magmatism. Hydrothermal systems form
anywhere that hot water, heated by volcanic plumbing systems, moves through
rocks. Spectacular geysers at places like Yellowstone National Park in the
United States form when hydrothermal water erupts at Earth's surface.
-
- Finding a hydrothermal Martian zircon raises
the possibility of ore deposits forming on early Mars. Previous studies have proposed a wet
Pre-Noachian Mars. Unusual oxygen isotope ratios in a 4.43 billion-year-old
Martian zircon were previously interpreted as evidence for an early
hydrosphere. Mars may have had an early
global ocean 4.45 billion years ago.
-
- Magmatic hydrothermal systems were active
during the early formation of Mars' crust 4.45 billion years ago. It's not clear whether this means surface
water was stable at this time. What is clear is that the crust of Mars, like
Earth, had water shortly after it formed,
a necessary ingredient for habitability.
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November 27, 2024 MARS - had
water at one time? 4624
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--------------------- --- Wednesday, November 27,
2024
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