Mars Seen in Clear and Dusty Conditions
These side-by-side images of Mars, taken roughly two years apart, show very different views of the same hemisphere of Mars. Both were captured when Mars was near opposition, which occurs about every two years, when Earth’s orbit catches up to Mars’ orbit. At that time, the Sun, Earth, and Mars fall in a straight line, with Mars and the Sun on “opposing” sides of Earth.
The image on the left, taken on May 12, 2016, shows a clear atmosphere. The picture on the right, taken on July 18, 2018, features a global dust storm, with spring in the southern hemisphere.
Scientists believe that heat from the southern hemisphere’s spring and summer triggers dust storms that originate in the Hellas Basin, the lowest point on the planet.
Although the Red Planet is showing virtually the same face to us, classical dark features first mapped by early sky watchers look different in each image. This is partly because of obscuration from the 2018 global dust storm, but also because the northern hemisphere was tilted toward Earth in 2016, and away from Earth in 2018. The latter view reveals more of southern hemisphere, including the cloud-enshrouded south polar region.
The phenomenon of opposition is a result of the difference in orbital periods between Earth’s orbit and Mars’ orbit. While Earth takes the familiar 365 days to travel once around the Sun, Mars takes 687 Earth days to make its trip around our star. As a result, Earth makes almost two full orbits in the time it takes Mars to make just one, resulting in the occurrence of Martian oppositions about every 26 months.
Credits
NASA, ESA, and STScI| About The Object | |
|---|---|
| Object Name | Mars |
| Object Description | Planet |
| About The Data | |
| Data Description | The HST observations include those from program (M. Mutchler) |
| Instrument | WFC3/UVIS |
| Exposure Dates | July 18, 2018 |
| Filters | F275W, F410M, F502N, F673N |
| About The Image | |
| Color Info | This image is a composite of separate exposures acquired by the WFC3/UVIS instrument. Several filters were used to sample various wavelengths. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Purple: F275W Blue: F410M Green: F502N Red: F673N |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
