Lesson Two

The Tour and The North Polar Area

Review

Last lesson, we learned about the Ionian Coordinate system, the three most important volcanoes to know, and the nine regiones.  The features discussed in lesson one will be discussed again but I felt it was important that you have an idea as to where they are on Io.  After all of these lessons, we will return to those three and learn why there location is important.  The Ionian Coordinate system is important in getting an idea about the location of the volcanoes discussed in these lessons as well as the areas discussed.

The Tour

At first glance there seems to be no system to the lessons.  WRONG!!   Each lesson has a plot, an area on Io that we discuss.  All the volcanoes, mountains, plateaus, lava flows, and crater within that plot are discussed in each particular lesson.  What is the order of the lessons/plots?  Well, first we start at the north pole, this lesson, and then we go south then east starting at the 0 W.

Click for caption and full-resolution image

The above image shows each plot, also known as a quadrangle, that will be discussed in the and the 14 following lessons.  As stated above, we begin on this page with the north pole, or Quadrangle Ji-1, and will continue with Quadrangle Ji-5 in Lesson Three.  The following is a schedule for the next 14 lessons:

I wish to acknowledge A. Tayfun Owen and Calvin Hamilton for providing the images of the Ionian quadrangles!

The North Polar Region

Click for caption and full-resolution image

The first area discussed in this Ionian Geography Review is the North Polar Region otherwise known as quadrangle Ji-1.  This region covers all longitudes and latitudes 65.5 deg. North to the north pole (90 deg. North).

There are very few known features in the north polar region. This is due to the poor coverage at north polar latitudes.  In fact, most of the area north of 80 deg. North has never been imaged.  This is seen as a large dark area at the center of the above image   In the above image, the prime meridian is the straight line running down from the pole, 270 deg. is the straight line running right from the pole, 180 deg. is the straight line running up from the pole, and 90 deg. is the straight line running left from the pole.  Longitude is marked every 30 deg. and latitude is marked every 10 deg.

Though they are few and far between in the north polar area, there are a few interesting features in this area.  They are all unnamed.  The first is an unnamed lava flow at 70 deg. North and 30 deg. west.  This volcano erupted on October 6, 1996 at a temperature of 1350 K.  The size of the lava flow at this temperature was determined to be 15.2 sq. km.  The temperature could well have been hotter but due to its northern location it could not be better determined.  This eruption was believed to be a Tvashtar-type lava fountain leading to a theory that these kinds of eruptions take place most commonly near the poles.  Tvashtar Catena will be discussed in lesson five.  The eruption also produced a new bright deposit.

Another feature in this quadrangle is a caldera at 75 deg. North and 295 deg. West.  This caldera has never been the site of a hotspot nor has it been the site of a surface change.  The Northern portion of Lei-Kung Fluctus can be seen at the right part.  This large lava flow from the '60's and '70's reaches all the way down to 45 deg. North from a vent at 65 deg. North, 195 deg. West.  Bright white deposits can be seen north of the vent of Lei-Kung in this quadrangle near the top of the image.  Also, another caldera can be seen north of these deposits at 74 deg. North and 195 deg. West.  Another feature that can be seen in this image is the northern fringes of Tvashtar Catena on the upper left edge of the image.  This volcano will be discussed in Lesson five.

Click this image for a high-resolution view

An unnamed volcano just north of Tvashtar Catena is in this quadrangle.   The albedo of this caldera darkened between early July 1999 during the C21 orbit and mid-February 2000 during the I27 flyby of Io.  This indicated that an eruption occurred at this volcano during that time that covered the caldera floor in lava flows.   It is not known when this eruption took place.

As you can see, not much is known about the North polar region of Io.   This will change however.  On August 6, 2001, Galileo is tentatively scheduled to fly over the north pole region at a distance of a scant 100 km taking images as high as 1.5 m/pixel resolution.  Also, Galileo may take images of the unimaged region at the north pole.  Hopefully, Galileo will still be around to perform this flyby.

In the next lesson, we will discuss the Amaterasu-Dazhbog region of Io.