planetary science

All posts tagged planetary science

A plexiglass replica of Voyager's golden record.

A plexiglass replica of Voyager’s golden record by Steve Vance and others.

The first day of the DPS meeting was wall-to-wall with science. There were several talks about exoplanets or planets outside of our solar system, and at least one stuck out especially to me.

Christopher Spaulding of Caltech discussed the so-called “Kepler Dichotomy“. This cryptic phrase refers to a strange finding from the Kepler Mission.

Kepler discovers planets using the transit technique (i.e., by looking for a planet’s shadow as the planet passes in front of its star), and so we expect only to find a small fraction of planets in our galaxy this way since it’s unlikely for a planet’s orbit to be aligned just right for a transit.

In fact, Kepler found lots of systems in which several planets transit. By looking at these systems, we can estimate how many systems should have just one planet that we can see transiting. When we do, it turns out that Kepler discovered lots more such single planets that we would expect.

This result has led some astronomers to suggest that these singly-transiting systems might have formed in a different (“dichotomous”) way from the multi-transiting systems. Instead, Spaulding suggested that culprit behind this planetary mystery was the host star.

In his talk, Spaulding pointed out that, during their youths, these stars spun fast enough that they bulged out at their equators. These equatorial bulges tugged gravitationally on their planets, causing the orbits of planets closest to the stars to re-align and leaving the orbits of planets farther away alone.

The closest planets just happen to transit, but, because the orbits of their sibling planets are aligned differently, we just can’t see them via transit. Like a lot of exoplanet research, Spaulding’s work shows that planetary systems, especially in their youth, can be dynamic, even violent, places for planets to grow up in, far from the clockwork universe Newton envisioned.

Quilling moon by Jen Grier (@grierja).

Quilling moon by Jen Grier (@grierja).

In addition to science talks, the DPS meeting has begun hosting an astronomy art show. The same folks who collect planetary spectra and analyze photometric light curves also make some beautiful art, and one of the neatest works on display was a quilling (rolled paper art) image of the lunar surface.

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I’m in beautiful (if not, totally sunny) California this week for the American Astronomical Society’s Division of Planetary Sciences annual meeting.

Before the meeting officially starts on Monday, I helped organize the DPS Educators’ Workshop, a DPS tradition where planetary science-types work with local school teachers to explain the most recent science and help them develop lesson plans and activities for their students.

We spent several hours with teachers from all over SoCal and discussed lots of great activities, but one of the most popular and visually appealing is the Art and Astronomy activity.

For this activity, we invite the teachers to recreate space-based images of planetary surfaces using pastels. As usual with this activity, the teachers at first demured but ended up creating stunning and vibrant images of craters, geysers, and river deltas.

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Artist's depiction of ancient snowball Earth. From http://ichef.bbci.co.uk/naturelibrary/images/ic/credit/640x395/s/sn/snowball_earth/snowball_earth_1.jpg.

Artist’s depiction of ancient snowball Earth. From http://ichef.bbci.co.uk/naturelibrary/images/ic/credit/640×395/s/sn/snowball_earth/snowball_earth_1.jpg.

I sat in on a fascinating seminar today in the Geosciences Dept. given by Prof. Carol Dehler of Utah State University about statigraphic and isotopic evidence for a snowball Earth event.

Over its 4.5 billion year history, the Earth has probably experienced at least one, maybe more, severe glaciation events, during which ice covered more or less the whole Earth’s surface.

These events were probably very challenging for ancient Earth life, and some of the best documented events occurred at the end of the Neoproterozoic, about 540 million years ago, probably driving mass extinctions and possibly kicking off the Cambrian explosion in animal life.

In her presentation today, Prof. Dehler discussed her extensive field and laboratory studies of statigraphic deposits in the western US, laid down about this time in Earth’s history, deposits she calls ChUMPs.

While the ChUMP layers were building up, the Earth was going through dramatic geological and climatic variations. The ancient supercontinent of Rodinia was breaking up, and Dehler can see evidence of volcanism that accompanied this rifting as huge excursions in carbon isotopes locked up in the ChUMP deposits.

The carbon dioxide injected by these large eruptions probably also drove climate change, raising global temperatures, which caused rapid weathering of rocks that locked up the excess carbon dioxide in the rocks.

With so much CO2 sucked out the atmosphere, it’s possible the Earth then underwent rapid cooling, and this is what could have driven Earth into a snowball state during the Neoproterozoic.

However, the story told by the rocks and their isotopic compositions is complicated, and it’s not entirely clear whether the enhanced volcanism preceded the snowball Earth event: The ages attributed to the rocks still have uncertainties that are too large to be sure.

In any case, Dehler presented a compelling, complex story about the Earth’s ancient history, meticulously pieced together, one mineral grain at a time.