November 11, 2016 | David F. Coppedge

Activity on Planets Suggests Youth

Can these processes really have gone on for billions of years?

Mars Eruptions

Mars has polar caps of frozen carbon dioxide that wax and wane through the planet’s seasons. The Mars Reconnaissance Orbiter (MRO) has been watching the seasonal changes with its HiRISE camera for a decade now. A new paper published in Icarus reports the discovery of new troughs seen forming in polar terrain due to explosive jetting of CO2 as the ice sublimates in the Martian summer. The jets deposit mineral dust and sand on top of the ice, but also carve troughs in the terrain under the ice, creating branching patterns unique to Mars (see example on UAHiRISE page).

These jets and the related sub-ice gas flows are believed to carve troughs in the underlying polar deposits which, after multiple repetitions of this process throughout Martian spring seasons, create araneiform [spider-like] terrains….

Detection of the present day erosion working in polar areas and creating new topographical features is important for understanding of the processes that shape polar areas. Several years of HiRISE observations provide us with the information about the current rate of erosion and hence help estimate minimum ages of the araneiforms and the surface into which they are carved to be 1.3 × 103 Martian years.

Since a Martian year is about 1.88 Earth years, these erosional features are only about 2,500 years old. There is undoubtedly some cycling of material year by year, as new patterns erase old ones. But for this to have been going on for 4.5 billion years (the assumed age of the solar system), the material would have been recycled 1.8 million times by now.

Last year, Space.com reported that the Martian atmosphere is being lost to space. NASA’s MAVEN mission, sent to study the Martian atmosphere, surprised astronomers at the amount of loss. It makes it harder to believe enough CO2 remained to create the troughs over and over almost 2 million times.

But MAVEN results announced Thursday (Nov. 5 [2015]) show that the planet’s CO2 went up rather than down: Shortly after Mars’ global magnetic field shut down about 4.2 billion years ago, the solar wind and powerful sun explosions stripped away most of the planet’s atmosphere, sending it off into space….

“It’s not there,” he said of the atmospheric CO2 during NASA’s news conference Thursday announcing the MAVEN results. “It’s been removed from the solar system entirely, so it’s not possible to bring it back.

In another paper on Icarus (open access), scientists attempted to duplicate the explosive CO2 eruptions in the lab. They could only get the eruptions to occur under special conditions. “We have reproduced dust eruptions from a layer of dust inside a CO2 ice slab under Martian conditions,” they say. “We found that in order to trigger dust eruptions a delicate balance between pressure and temperature near the equilibrium of the CO2 phase change seems to be necessary.” Does that imply that the eruptions we observe today have only started recently? Generally speaking, secular scientists do not like to invoke special conditions for rare phenomena (e.g., Saturn’s rings, the Enceladus geysers, or the Martian jets) that just happen to occur when human beings are lucky enough to witness them.

Venus Volcanoes

“Volcanoes on Venus Erupted Recently, New Study Suggests.” That’s a headline on Space.com that revisits the mystery of Venus volcanism. Planetary scientists have been baffled by evidence from the Magellan orbital radar mapper in the late 1990s that suggested the entire surface of Venus had been resurfaced by rampant volcanism relatively recently in its assumed 4.5-billion-year history (see “Earth’s ugly sister can’t get a date,” 8/16/04, and follow-up reference, 8/27/09 ). It’s been particularly hard to explain in the absence of plate tectonics. A follow-up question has been whether the volcanoes are still active now, but it’s been hard to tell because of the planet’s thick, hot atmosphere. This article reports a “hotspot” that could be as young as yesterday.

Volcanic activity on Venus took place in the recent past, geologically speaking, and may still be happening on the planet today. New research takes a deeper look at one recent eruption on Venus’ surface.

The Idunn Mons volcano in the southwestern hemisphere of Venus rises 1.6 miles (2.5 kilometers) above the surrounding plains. In 2010, observations by the European Space Agency’s Venus Express probe revealed that Idunn Mons is a “hotspot,” meaning it radiates high levels of infrared light compared to the surrounding area. That suggests that lava flowed at the spot recently, and that the area is still warm.

Now, a more nuanced look at Idunn Mons suggests that the hotspot observations are consistent with multiple (cooled) lava flows along the volcano’s eastern flank, the new research shows. The researchers behind the new work said the finding suggests that Venus’ volcanos were active in the relatively recent past, and may still be active today.

Comet Tales

The Rosetta mission is complete, but analysis of the data on Comet 67P/Churyumov-Gerasimenko (Chury for short) will continue for years. One surprise was reported by Science Daily: “Comet Chury is much younger than previously thought.” How much younger? “the comet in its present form is hardly more than a billion years old.” Sounds pretty old, but that would be just 22% of the assumed 4.5-billion-year age. What happened after 78% of its life had transpired?

Analysis of the “neck” between the two lobes of the duck-shaped comet shows that it is too delicate to have survived the many collisions it should have suffered throughout its existence. To rescue the assumed age, they invoke a finely-tuned collision in its senior years, not enough to blast the comet to smithereens but strong enough to break it apart. That resulted in the two lobes separating, then recombining by gravity. It must be remembered, however, that comets lose material each time they come near the sun.

A paper in Nature reports on observations of the dust on Comet Chury. “Comets are thought to preserve almost pristine dust particles,” the Rosetta scientists begin, proceeding to interpret contradictory evidence about their building blocks. Previous missions found processed material that could not be considered pristine. Rosetta’s in-situ measurements show a hierarchical pattern of dust grains that the astonomers interpret as consistent with interplanetary dust particles from which the solar system presumably condensed. That, however, sounds circular; they are pristine, therefore we interpret them to look pristine. Some processing of theory appears to be in progress. Commenting on the paper in Nature, Ludmilla Kolokolova concludes,

The authors’ results enhance our fundamental understanding of cometary dust, and the processes that ultimately gave rise to planetary systems such as the Solar System. Their discovery of a hierarchical structure in cometary dust particles and their description of the basic building blocks of such particles might lead physicists to reconsider the interpretation of data obtained from ground-based observations of comets and re-evaluate the processes in protoplanetary nebulae — and will probably give rise to new models of how planets were formed.

How Planets Were Formed

But do astronomers really know much about how planets formed? We conclude this entry with a link to Science Daily that overthrows previous speculations about planets condensing out of stellar disks. Scientists got all excited last March about a putative “protoplanetary disk” forming around star TW Hydrae. Gaps in the disk seemed to be orbits where new planets were accreting. Sorry, the article concludes: it’s not the birth of a solar system, but likely its death. Photoevaporation in the disk from starlight is likely causing the disk to dissipate.

Destructive processes – recent processes – special epochs in planetary history: these are not predictions of secular models. They are anomalies requiring theory rescue devices. A simple look at the evidence suggests that real physical processes are tearing down order, not creating it, and doing it in far less time than billions of years.

 

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