How table accessibility can be improved?

It can be improved by connecting cells and headers.

Using the scope attribute and the headers attribute:

<table>
    <tr>
        <th scope="row">Mars</th>
        <td>.95</td>
        <td>.62</td>
        <td>5</td>
        <td>6</td>
        <td>7</td>
        <td>8</td>
        <td>9</td>
    </tr>
    <tr>
        <th id="diameter">Diameter measured in earths</th>
        <td>1</td>
        <td>2</td>
        <td>3</td>
        <td headers="diameter">.38</td>
        <td>4</td>
        <td>5</td>
        <td>6</td>
    </tr>
</table>