Redo some of the  documentation screenshots for Marble (English language) because they are outdated. Get a recent Marble (4.7). Set your KDE with default style, color, window decorations and fonts. In System Settings, set the style and color for KDE to "Oxygen" (Ubuntu has no KDE default colors!)  Use KSnapshot and read http://l10n.kde.org/docs/screenshots.php in order to redo the screenshots in png format with the default KDE theme and windows decoration. Name the screenshots exactly as they are named.
In this page, https://projects.kde.org/projects/kde/kdeedu/marble/repository/revisions/master/show/doc redo all screenshots that are more than one year old.

Expected results: upload the new screenshots as an archive (tar or zip)

Prerequisites: preferably look at Marble user manual prior to doing the task, read the page above about doing screenshots.