Fly Around the Solar System

Voyager 2 looking back at the planets in Eyes on the Solar System.

NASA’s new beta version of Eyes on the Solar System, developed by the Jet Propulsion Laboratory and Caltech, lets you do just that. The web application is essentially a 3D model of the solar system, containing many of its bodies and a great number of space probes sent out from Earth (including Epoxi 2, which recently performed a flyby of comet Hartley 2). With a number controls, you can zoom around the solar system exploring these objects, with beautiful 3D models for each of them. You can also manipulate the time to explore where the objects and the probes were in the past, or where they will be in the future.

Overall, this is a very glorious and well done project. It’s already a great tool for learning more about our planet's local neighborhood, and as it accumulates even more data and more components of the solar system, it can only get better. I can’t wait until this project leaves beta status, and includes further inclusions like nebulae and galaxies. You can head over to the project site right now to try it out. You will have to install the Unity Web Player plug-in in order to use it, and you will be prompted to install it on the site.

Cassini and Saturn in Eyes on the Solar System

Halley's Comet in Eyes on the Solar System

Equinox on Saturn

About every 15 Earth years, Saturn’s experiences an equinox, much like Earth’s equinox. On Earth it occurs twice in Earth’s orbit—two times every Earth year—when the Sun lies in the Earth’s equatorial plane. As a result, the duration of day and night are approximately equal, which is also the origin of the term equinox.

Saturn also experiences this twice in its orbit, but its orbit lasts about 30 Earth years, meaning that the equinox takes place every 15 Earth years. Plus, this event is even more special on Saturn. Saturn has a very famous and widely recognized set of rings. These rings lie in Saturn’s equatorial plane, and therefore, when Saturn undergoes an equinox, the Sun also lies in the plane of the rings. Since the rings are very thin (at least compared to the size of Saturn), during the equinox the shadow from the rings disappears. The rings themselves also are barely visible because only the edges catch the light of the Sun.

The Cassini Spacecraft was present to capture photos from the most recent equinox last August. The below photograph was just recently released by the Jet Propulsion Laboratory, captured on July 18, 2009, just a few weeks before the equinox. The barely visible rings cast a thin shadow on the body of Saturn, creating a stunning view. In fact, the rings captured in the original images from Cassini were so dim that it was necessary to brighten them by a factor of 9.5 relative to the planet in order to produce the result (I’d be very interested to see the picture where the rings are not brightened).

The picture below is from just after equinox, when the shadow from the rings on Saturn is barely visible. Again, the brightness of the rings relative to the planet had to be increased in order to generate the image.

This equinox was also important in allowing Cassini to gather important data about the structure of the rings. When the rings are at a large angle to the Sun, small bumps and features are very hard to detect. However, when the Sun’s rays are parallel to the plain of the rings, the bumps and features create large shadows which are much easier to detect. And the results from this work were surprising. Some areas of Saturn’s rings ripple up and down, forming vertical formations about 800 km high. This phenomenon has not been explained yet. Meanwhile in some other areas, the particles in the ring are affected by the gravity of moons of Saturn, towering above the plain as high as 4 km. So while the rings may appear simple and peaceful in the images above, they have some very complex and strange features.

Permanently Stationary Spirit

Spirit's Last Tracks Before It Got Stuck
NASA/JPL-Caltech

Previously, I wrote about the Mars Exploration Rover Spirit being embedded in a patch of rocky Martian soil. NASA today designated Spirit to be no longer fully mobile. The decision is taking place after months of effort and numerous commands for movement that have failed at moving the robot.

Spirit's Rocky Situation

Spirit, one of the Mars Exploration Rovers, is in a very rocky situation. Since April 2009, the rover has been embedded in a patch of rocky Martian soil. The dark and crusty ground, captured in the picture above by Spirit before its current predicament, broke through under the rover's wheels to reveal loose sandy soil, which trapped the wheels. Furthermore, when Spirit photographed its undercarriage (image at right) with its robotic arm, it revealed a rock potentially touching the robot.

A Large Planet Orbiting a Small Star

An artist's conception of the planetary system.

Astrometry, a 50 year old technique used to find exoplanets, planets around other stars, has finally succeeded. Planets outside the solar system are nearly impossible to see, so the method relies on measuring the movements of a star moving back and forth due to its planet. This technique requires numerous careful and precise measurements, and these have to be compared to many others taken over long periods of time. This is why, until now, the method has failed to provide any conclusive evidence towards exoplanets.

Using the Palomar Observatory near San Diego, fitted with an astrometry instrument, a two astronomer team from NASA's Jet Propulsion Laboratory (JPL) have conducted rigorous observations for 12 years. They have studied 30 different stars, and from that number, a new exoplanet has been discovered around one of them.

The planet, VB 10b, is very large and somewhat like the planet Jupiter in our own solar system. It has a mass six times that of Jupiter's, but generates its own internal heat, putting its temperature near the Earth's.

Compared to the planet, its star, VB 10, itself is tiny. It is a twelfth of the mass of the Sun. This is greater than its planet's mass, but the size of the star itself is about the same as its planet. The star used to be the smallest known star, and now is the smallest star known to possess a planet. The importance of the finding is that planets might be very common, even existing around smaller stars like VB 10. "This is a hint that nature likes to form planets, even around stars very different from the sun," states Wesley Traub, chief scientist for NASA's Exoplanet Exploration Program at JPL.

The star's smaller size indicates that it is in the center of a small planetary system. Rocky planets like the Earth would lie between VB 10b and VB 10. The finding indicates that astrometry is capable of finding planetary systems arranged like ours, because it locates planets similar to Jupiter.

In addition to astrometry, other methods of finding exoplanets exist. The radial velocity method analyzes the Doppler shifts in a star's light resulting from a planet tugging on it. The transit method, employed by the Kepler mission, looks at the dips of light that occur when a planet passes in front of its star.

Images: JPL-Caltech/NASA

Astronomy and Space celebrates International Year of Astronomy 2009.

"Mission Accomplished, but New Questions Await!"

That's what NASA is announcing about their Cassini mission. Today, on June 30, Cassini is ending its primary mission, lasting for four years. But Cassini is not done with Saturn and its moons. There is still much too left to learn about Saturn, and the primary mission was just the start.

Now, Cassini starts a new journey, with a new two-year mission. This extended mission, called the Cassini Equinox Mission, was approved in April. After Cassini unleashed new information about Saturn's moons Titan and Enceladus, these two moons became the prime targets for te extended mission. The mission will also focus on the seasonal effects on Titan and Saturn, and looking and analyzing the geometry of the rings of Saturn during the Saturn equinox in August 2009, when sunlight will pass directly through the plane of the the rings.

Find out more about Cassini at NASA and JPL.

Image from NASA/JPL.

Seven Minutes of Terror!

Seven Minutes of Terror!

That's what the spacecraft and the team working on the Phoenix spacecraft will go through, when Phoenix attempts a landing this Sunday on Mars. This is when the space vehicle will first hit the atmosphere of Mars, go through parachute deployment, and finally hit the surface, with many more things in between. However, since signals between the Earth and Mars take about ten minutes to travel, the crew working on Phoenix will get the first signals that the landing process has started, after the whole landing sequence has actually ended! So how will Phoenix try to avoid the fate of many previous Martian missions and not splatter on the ground?

Phoenix will have the support of three Mars orbiters, that are currently circling the planet, NASA's Mars Reconnaissance Orbiter and the Mars Odyssey and ESA's Mars Express. The signals sent by Phoenix during its entry on to Mars will rely on the successful relay of the message to Earth by these orbiters. This is the first time any Mars lander will have the support of the relay system, both for landing and on the surface.

First, Phoenix will enter the Martian atmosphere at 21,000 km/h (13,000 m/h). A parachute, very similar to the Viking spacecrafts', will open at 12.6 km (7.8 miles) above Mars. The parachute will slow down the hurtling spacecraft with drag. Meanwhile, as Phoenix will near the surface, an onboard radar will give the altitude and velocity of the descent of the Phoenix spacecraft, allowing the onboard computer to make adjustments as necessary. This step is necessary, since upon entering and until the parachute opening, big errors in positioning can be made.

After two minutes of descent with the parachute, Phoenix will jettison its back shell, to which the parachute is attached. Then Phoenix will free fall, for half a second, towards the surface of Mars, and then ignite its engines. Nine engines from the total twelve will pulse for 10 seconds. The remaining three will fire steadily, for stability. Right before touchdown, as a finishing touch, the vehicle is turned, to increase the amount of sunlight that will fall on the solar panels.

The Jet Propulsion Laboratory will be able to give course adjustments if necessary up to three hours before Phoenix lands on Mars. However, during the landing, these people can only stand back, watch and hope, while they endure the seven minutes of terror.

The following video shows an animated launch and landing of the Phoenix, and gives a very nice visual of the above process:

Image from NASA.